Coalescing filter media

ABSTRACT

Filter media, filter elements, and methods for filtering an gas stream are described herein. In some embodiments, the filter media may comprise a fiber web comprising a plurality of fibers and having a particular oil repellency level. For instance, in certain embodiments, the surface chemistry of the fiber web may be tailored to impart a particular surface energy density that matches the surface energy density of the fluid (e.g., an oil, a lubricant, and/or a cooling agent) being removed from the gas stream. In some embodiments, the fiber web may be wrapped around a core. For example, the fiber web may be wrapped around the core such that it forms two or more layers around the core. In some cases, the fiber web may be perforated. In certain embodiments, an gas stream comprising a fluid (e.g., an oil, a lubricant, and/or a cooling agent) may be passed through the fiber web, filter media, and/or filter element such that at least a portion of the fluid coalesces on the fiber web. Fiber webs, filter media, and/or filter elements as described herein may be particularly well-suited for applications that involve filtering gas streams containing oil, lubricants, and/or cooling agents (e.g., gas streams generated by a compressor) though the media may also be used in other applications. Advantageously, the fiber webs, filter media, and/or filter elements described herein may significantly reduce or prevent fouling of the filter caused by oil or other liquids.

FIELD OF INVENTION

The present embodiments relate generally to coalescing filter media, andspecifically, to coalescing filter media having enhanced oil repellencylevels and/or performance characteristics, and related methods.

BACKGROUND

Filter elements can be used to remove contamination in a variety ofapplications. Such elements can include a filter media which may beformed of a web of fibers. The fiber web provides a porous structurethat permits fluid (e.g., gas, liquid) to flow through the media.Contaminant particles (e.g., dust particles, soot particles) containedwithin the fluid may be trapped on or in the fiber web. Depending on theapplication, the filter media may be designed to have differentperformance characteristics.

Although many types of filter media for filtering oil from gas streamsexist, improvements in the physical and/or performance characteristicsof the filter media (e.g., strength, air resistance, efficiency, andhigh dust holding capacity) would be beneficial.

SUMMARY OF THE INVENTION

Coalescing filter media and related methods are generally provided. Thesubject matter of this application involves, in some cases, interrelatedproducts, alternative solutions to a particular problem, and/or aplurality of different uses of structures and compositions.

In one aspect, methods for filtering an oil, lubricant, and/or coolingagent from a gas stream are provided. In some embodiments, the methodcomprises passing the gas stream including the oil, lubricant, and/orcooling agent through a filter element, wherein the filter elementcomprises a fiber web wrapped around a core such that at least twolayers of the fiber web are formed, the fiber web comprising a pluralityof fibers having an average fiber diameter of at least 0.01 microns andless than or equal to 50 microns, a basis weight of at least 1 g/m² andless than or equal to 270 g/m², and, a thickness of at least 0.01 mm andless than or equal to 5.0 mm, wherein the fiber web has an oilrepellency level of between 4 and 6, wherein the fiber web has an oilcarry over of less than 20%, and wherein the oil, lubricant, and/orcooling agent has a surface tension of between 22 mN/m and 33 mN/mmeasured at 23° C. and 50% RH.

In some embodiments, the method comprises passing the gas streamincluding the oil, lubricant, and/or cooling agent through a fiber web,wherein the fiber web comprises a plurality of fibers having an averagefiber diameter of at least 0.01 microns and less than or equal to 50microns, a basis weight of at least 1 g/m² and less than or equal to 270g/m², and a thickness of at least 0.01mm and less than or equal to 5.0mm, wherein the fiber web has an oil repellency level of between 4 orgreater and 6 or less, and wherein the fiber web comprises a pluralityof perforations having an average cross-sectional dimension of at leastabout 1 mm.

In another aspect, filter elements are provided. In some embodiments,the filter element comprises a core and a fiber web wrapped around thecore such that at least two layers of the fiber web are formed, whereinthe fiber web comprises a plurality of fibers having an average fiberdiameter of at least 0.01 microns and less than or equal to 50 microns,a basis weight of at least 1 g/m² and less than or equal to 270 g/m²,and a thickness of at least 0.01mm and less than or equal to 5.0 mm,wherein the fiber web has an oil repellency level of between 4 orgreater and 6 or less, and wherein the fiber web has an oil carry overof less than 20%.

In yet another aspect, filter media are provided. In some embodiments,the filter media comprises a fiber web, wherein the fiber web comprisesa plurality of fibers having an average fiber diameter of at least 0.01microns and less than or equal to 50 microns, a basis weight of at least1 g/m² and less than or equal to 270 g/m², and a thickness of at least0.01mm and less than or equal to 5.0 mm, wherein the fiber web has anoil repellency level of between 4 or greater and 6 or less, and whereinthe fiber web comprises a plurality of perforations having an averagecross-sectional dimension of at least about 1 mm.

Other advantages and novel features of the present invention will becomeapparent from the following detailed description of various non-limitingembodiments of the invention when considered in conjunction with theaccompanying figures. In cases where the present specification and adocument incorporated by reference include conflicting and/orinconsistent disclosure, the present specification shall control. If twoor more documents incorporated by reference include conflicting and/orinconsistent disclosure with respect to each other, then the documenthaving the later effective date shall control.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting embodiments of the present invention will be described byway of example with reference to the accompanying figures, which areschematic and are not intended to be drawn to scale. In the figures,each identical or nearly identical component illustrated is typicallyrepresented by a single numeral. For purposes of clarity, not everycomponent is labeled in every figure, nor is every component of eachembodiment of the invention shown where illustration is not necessary toallow those of ordinary skill in the art to understand the invention. Inthe figures:

FIG. 1 is a schematic diagram showing a cross-section of a filter mediaaccording to one set of embodiments;

FIG. 2 is a schematic diagram showing a perspective view cross-sectionof a filter according to one set of embodiments;

FIG. 3 is a schematic diagram showing a cross-section of a filteraccording to one set of embodiments;

FIG. 4 is a schematic diagram showing a cross-section of a filter mediaaccording to one set of embodiments;

FIG. 5 is a schematic diagram showing a perspective view cross-sectionof a filter according to one set of embodiments; and

FIG. 6 is a schematic diagram showing a perspective view cross-sectionof a filter according to one set of embodiments.

DETAILED DESCRIPTION

Filter media, filter elements, and methods for filtering a gas stream(e.g., air) are described herein. In some embodiments, the filter mediamay comprise a fiber web comprising a plurality of fibers and having aparticular oil repellency level. For instance, in certain embodiments,the surface chemistry of the fiber web may be tailored to impart aparticular surface energy density that matches the surface energydensity of the fluid (e.g., an oil, a lubricant, and/or a cooling agent)being removed from the gas stream. In some embodiments, the fiber webmay be wrapped around a core (e.g., an inner core). For example, thefiber web may be wrapped around the core such that it forms two or morelayers around the core. In some cases, the fiber web may be perforated.In certain embodiments, an gas stream comprising a fluid (e.g., an oil,a lubricant, and/or a cooling agent) may be passed through the fiberweb, filter media, and/or filter element such that at least a portion ofthe fluid coalesces on the fiber web. Fiber webs, filter media, and/orfilter elements as described herein may be particularly well-suited forapplications that involve filtering gas streams containing oil,lubricants, and/or cooling agents (e.g., gas streams generated by acompressor) though the media may also be used in other applications.Advantageously, the fiber webs, filter media, and/or filter elementsdescribed herein may significantly reduce or prevent fouling of thefilter caused by oil or other liquids and/or increase the coalescenceand/or continuous removal of the oil or other liquids.

An example of a filter element including a fiber web and a core) isshown in FIG. 1. In some embodiments, the fiber web may be adjacent(e.g., directly adjacent) the core. As shown illustratively in FIG. 1, afilter element 100, shown in cross section, may include a fiber web 110comprising a plurality of fibers and a core 120 directly adjacent fiberweb 110. In some embodiments, the fiber web may be wrapped around thecore. For example, as shown illustratively in FIG. 2, filter element 102comprises fiber web 110 wrapped around core 120 (e.g., a non-fibrouscomponent, such as a core). In certain embodiments, the fiber web iswrapped around the core such that the fiber web substantially covers atleast a portion of the surface of the core along a circumference of thecore. In some embodiments, the fiber web is wrapped two or more timesaround the core. For example, in certain embodiments, the filter elementcomprises at least two layers of the fiber web wrapped around the core.The core may comprise, for example, a wire mesh or a perforated sheet,and may be formed of metal or plastic in some embodiments. Additionalexamples of cores are described in more detail below.

As used herein, when a layer is referred to as being “adjacent” anotherlayer, it can be directly adjacent to the layer, or an intervening layeralso may be present. A layer that is “directly adjacent” another layermeans that no intervening layer is present.

As shown illustratively in FIG. 3, filter element 106 comprises fiberweb 110 wrapped around core 120 such that filter element 106 comprisestwo layers of fiber web 110. In some embodiments, the fiber web iswrapped continuously around the core. That is to say, in some suchembodiments, a single fiber web may be wrapped around the core such thatat least one continuous layer is formed. In some embodiments, the singlefiber web may be wrapped around the core such that at least two layersof the single fiber web are formed. In some embodiments, the filterelement may comprise at least 1, at least 2, at least 3, at least 4, atleast 5, at least 7, at least 9, at least 10, at least 11, at least 13,at least 15, at least 17, or at least 19 layers of the single fiber webwrapped around the core. In certain embodiments, the filter elementcomprises less than or equal to 20, less than or equal to 19, less thanor equal to 17, less than or equal to 15, less than or equal to 13, lessthan or equal to 12, less than or equal to 11, less than or equal to 10,less than or equal to 9, less than or equal to 7, less than or equal to5, less than or equal to 4, less than or equal to 3, or less than orequal to 2 layers of the single fiber web wrapped around the core.Combinations of the above-referenced ranges are also possible (e.g., atleast 1 layer and less than or equal to 20 layers, at least 2 layers andless than or equal to 13 layers, at least 2 layers and less than orequal to 4 layers, at least 5 layers and less than or equal to 10layers). Other ranges are also possible.

The fiber web may have any suitable configuration with respect to thecore. For instance, it should be understood that the fiber web need notwrapped around a core in all embodiments. For example, in certainembodiments, one or more layers comprising the fiber web may be disposedwithin a core (e.g., an outer core).

Configurations of the fiber web may also vary. For example, in someembodiments, one or more layers comprising the fiber web may be directlyadjacent one or more support layers. The support layer may comprising amesh and/or a plurality of fibers such as synthetic fibers, cellulosefibers, and/or glass fibers as described in more detail below. In someembodiments, a filter element or filter media comprising the fiber webmay comprise two or more support layers. The support layer(s) may bepositioned upstream and/or downstream of the fiber web layer(s). In someembodiments, the fiber web layer(s) along with the support layer(s), ifpresent, may be wrapped around a core in a filter element. The fiber webmay be adhered to the support layer(s) by any suitable means including,for example, by lamination, point bonding, thermo-dot bonding,ultrasonic bonding, calendering, use of adhesives (e.g., glue-web),and/or co-pleating.

In some embodiments, the fiber web layer(s) along with the supportlayer(s), if present, may be pleated (e.g., co-pleated). In some suchembodiments, the pleated layers may be positioned adjacent a core (e.g.,wrapped around a core).

The core can have any cross-sectional shape (circular, oval, triangular,irregular, trapezoidal, square or rectangular, or the like). The coremay also have an aspect ratio (length to average cross-sectionaldimension) of at least 1:1, at least 2:1, more typically at least 3:1,5:1, or 10:1 or more. The fiber web may at least partially or completelycover the core.

It has been discovered within the context of certain embodimentsdescribed herein, that the oil repellency level of the fiber web allowsadequate coalescence to be achieved without increasing (or minimallyincreasing) the resistance of the fiber web and/or the overall filtermedia. Without wishing to be bound by any theory, it is believed thattailoring the surface chemistry of the fiber web (e.g., by modificationof the fiber web and/or choosing appropriate fiber materials) allows thefluid in the gas stream (e.g., the fluid to be separated comprising anoil, lubricant, and/or cooling agent, etc.) to favorably interact withthe surface, such that the surface energy density (or surface tension)is changed relative to the surface energy density of fiber web. Having asimilar surface energy density between the fluids in the gas stream andthe surface of the fiber web causes the fluid to be separated topreferentially associate with (e.g., wetting) the fiber web.

The fiber web may be tailored to have a particular oil repellency level,e.g., in order to coalesce oil, lubricants, and/or cooling agents froman gas stream passed through the fiber web. In some embodiments, the oilrepellency level of the fiber web is between 4 and 6 (e.g., 4-6,4.5-5.5, 4.5-5, 5-5.5). In certain embodiments, the oil repellency levelof the fiber web is 4, 4.5, 5, 5.5 or 6. Oil repellency level asdescribed herein is determined according to AATCC TM 118 (1997) measuredat 23° C. and 50% relative humidity (RH). Briefly, 5 drops of each testoil (having an average droplet diameter of about 2 mm) are placed onfive different locations on the surface of the fiber web. The test oilwith the greatest oil surface tension that does not wet (e.g.,. has acontact angle greater than or equal to 90 degrees with the surface) thesurface of the fiber web after 30 seconds of contact with the fiber webat 23° C. and 50% RH, corresponds to the oil repellency level (listed inTable 1). For example, if a test oil with a surface tension of 26.6 mN/mdoes not wet (i.e. has a contact angle of greater than or equal to 90degrees with the surface) the surface of the fiber web after 30 seconds,but a test oil with a surface tension of 25.4 mN/m wets the surface ofthe fiber web within thirty seconds, the fiber web has an oil repellencylevel of 4. By way of another example, if a test oil with a surfacetension of 25.4 mN/m does not wet the surface of the fiber web after 30seconds, but a test oil with a surface tension of 23.8 mN/m wets thesurface of the fiber web within thirty seconds, the fiber web has an oilrepellency level of 5. By way of yet another example, if a test oil witha surface tension of 23.8 mN/m does not wet the surface of the fiber webafter 30 seconds, but a test oil with a surface tension of 21.6 mN/mwets the surface of the fiber web within thirty seconds, the fiber webhas an oil repellency level of 6. In some embodiments, if three or moreof the five drops partially wet the surface (e.g., forms a droplet, butnot a well-rounded drop on the surface) in a given test, then the oilrepellency level is expressed to the nearest 0.5 value determined bysubtracting 0.5 from the number of the test liquid. By way of example,if a test oil with a surface tension of 25.4 mN/m does not wet thesurface of the fiber web after 30 seconds, but a test oil with a surfacetension of 23.8 mN/m only partially wets the surface of the fiber webafter 30 seconds (e.g., three or more of the test droplets form dropletson the surface of the fiber web that are not well-rounded droplets)within thirty seconds, the fiber web has an oil repellency level of 5.5.

TABLE 1 Oil Repellency Surface tension Level Test Oil (in mN/m) 1 Kaydol(mineral oil) 31 2 65/35 Kaydol/n-hexadecane 28 3 n-hexadecane 27.5 4n-tetradecane 26.6 5 n-dodecane 25.4 6 n-decane 23.8 7 n-octane 21.6 8n-heptane 20.1

In some embodiments, as described in more detail below, the fiber webmay be used to decrease oil carry over of a filter media and/or filterelement. Briefly, oil carry over provides a measurement of oil that ispresent in an gas stream comprising the oil, after the gas stream haspassed through the fiber web. The decreased oil carry over may beachieved, in some embodiments, by tailoring the surface chemistry of thefiber web (e.g., by surface modification of a surface of the fiber weband/or by choosing a particular surface chemistry of the plurality offibers) to allow at least one surface of the fiber web to interact withone or more components (e.g., oil, lubricant, and/or cooling agents) inthe gas stream. The oil carry over may also be enhanced by the fiber webbeing wrapped at least two times around a core. In certain embodiments,the choice of surface chemistry (e.g., surface modification), fiberdiameter, mean flow pore size, and/or permeability of the fiber web maycause the fluid to be to coalesced into droplets that may be easilyseparated from the gas stream. In some embodiments, the fiber web asdescribed herein may be particularly well suited for removing dropletsof oil having a surface tension between 22 mN/m and 33 mN/m measured at23° C. and 50% RH by the Du Noüy ring method from an gas stream. Incertain embodiments, the fiber web may be particularly well suited forremoving droplets having relatively small diameters from the gas stream.

In certain embodiments, the filter media or filter element describedherein do not require separate stages of filter media, wherein eachstage serves a different purpose such as particle separation,coalescence, and/or shedding. For example, a single filter media caninclude one or more layers of fiber web that perform two or more ofthese functions (particle separation, coalescence, and/or shedding).However, in other embodiments, different stages of media may beincluded.

In some embodiments, the fiber web and/or a plurality of fibers withinthe fiber web may be modified to alter and/or enhance the wettability ofat least one surface of the fiber web with respect to a particular fluid(e.g., oil). For instance, in some embodiments, the surface modificationmay alter and/or enhance the hydrophilicity and/or lipophilicity of atleast one surface of the fiber web. In one example, a surface of arelatively lipophobic (or oleophobic) fiber web may be modified with alipophilic material (e.g., charged material, non-charged lipophilicmaterial, organic lipophilic material), such that the modified surfaceis lipophilic. In some such cases, the fiber web may have a modifiedlipophilic surface (e.g., upstream surface) and an unmodified lipophobicsurface (e.g., downstream surface). In other cases, the upstream anddownstream surfaces of the fiber web may be modified to be lipophilic.Alternatively, in certain embodiments, a surface of a relativelylipophilic fiber web may be modified with a lipophobic material, suchthat the modified surface is lipophobic.

In certain embodiments, both the upstream and the downstream surfaces ofa fiber web are modified. In other embodiments, the entire fiber web ismodified. Although other surface modification techniques can be used, incertain embodiments, a layer is modified using chemical vapordeposition. For instance, the fiber web may comprise a chemical vapordeposition coating.

Regardless of whether the surface is modified to lipophilic orlipophobic, in general, at least one surface of the fiber web may bemodified to be wetting toward the fluid to be separated. In someembodiments, at least one surface of the fiber web may be modified toenhance its wettability with respect to a particular fluid.

In some embodiments, the fiber web may serve to decrease the overall oilcarry over of the filter media and/or a filter element comprising thefiber web. For instance, the fiber web may be configured to effectivelycoalesce the fluid to be separated such that the filter media and/or afilter element may achieve a particular oil carry over. Oil carry over,as described herein, is measured according to ISO 12500 on a 6×10 cmfiber web with a 20 cm/s face velocity and a temperature of 40° C.,using a Shell Corona S2 P100 test oil at a concentration of 0.2 g/m³. Incertain embodiments, the fiber web has an oil carry over of less than orequal to 5000 mg/m³, less than or equal to 4000 mg/m³, less than orequal to 3000 mg/m³, less than or equal to 2500 mg/m³, less than orequal to 2000 mg/m³, less than or equal to 1500 mg/m³, less than orequal to 1000 mg/m³, less than or equal to 500 mg/m³, less than or equalto 250 mg/m³, or less than or equal to 100 mg/m³. In some embodiments,the fiber web has an oil carry over of greater than or equal to 0 mg/m³,greater than or equal to 100 mg/m³, greater than or equal to 250 mg/m³,greater than or equal to 500 mg/m³, greater than or equal to 1000 mg/m³,greater than or equal to 1500 mg/m³, greater than or equal to 2000mg/m³, greater than or equal to 2500 mg/m³, greater than or equal to3000 mg/m³, or greater than or equal to 4000 mg/m³. Combinations of theabove-referenced ranges are also possible (e.g., greater than or equalto 0 mg/m³ and less than or equal to 5000 mg/m³). Other ranges of oilcarry over are also possible.

In certain embodiments, a fiber web described herein has an oil carryover percentage of less than 20%. Oil carry over percentage, asdescribed herein, is a measurement of oil that is present in an gasstream comprising the oil, after the gas stream has passed through thefiber web, as a percentage of total oil present in the gas stream priorto passing through the fiber web. The oil carry over percentage isdetermined by measuring oil carry over values as described above. Insome embodiments, the fiber web has an oil carry over percentage of lessthan or equal to 20%, less than or equal to 15%, less than or equal to10%, less than or equal to 5%, less than or equal to 3%, less than orequal to 2%, or less than or equal to 1%. In certain embodiments, thefiber web has an oil carry over percentage of greater than or equal to0%, greater than or equal to 1%, greater than or equal to 2%, greaterthan or equal to 3%, greater than or equal to 5%, greater than or equalto 10%, or greater than or equal to 15%. Combinations of theabove-referenced ranges are also possible (e.g., less than or equal to20% and greater than or equal to 0%, less than or equal to 3% andgreater than or equal to 0%). Other values of oil carry over percentageare also possible.

In some embodiments, the fiber web may be perforated, i.e the fiber webmay comprise a plurality of perforations. In certain embodiments thefiber web may include a plurality of perforations as shownillustratively in FIG. 4. The perforations may, in some embodiments,reduce the overall pressure drop of the filter media/filter elementand/or impart a relatively high air permeability while allowing thefiber web to maintain good oil coalescence characteristics. Whenmultiple layers are present, the perforations may be positioned suchthat perforations between adjacent layers of fiber web do not align,e.g., when layered on a planar surface or wrapped around a core. Whilemuch of the description herein relates to a fiber web wrapped around acore, in some embodiments, a filter element or filter media comprises aperforated fiber web without a core. However, in alternativeembodiments, the perforated fiber web may be wrapped around a core, asdescribed above.

In some embodiments, perforating a fiber web may result in a pluralityof holes through the full thickness of the fiber web. In one embodiment,a plurality of perforations, as shown illustratively in a cross-sectionof fiber web 110 in FIG. 4, may define a plurality of perforations orholes 115. In certain embodiments, a perforation may have definedattributes, such as shape, size, aspect ratio, length, and/or width. Forexample, each perforation in the plurality of perforations may have adefined shape, which may be, for example, substantially circular,square, rectangular, trapezoidal, polygonal or oval in cross-sectionand/or in plane view (i.e., viewed from above). The shapes may beregular or irregular. Other shapes are also possible.

In some instances, the average largest cross-sectional dimension of theperforations (e.g., average diameter of the holes) may be measured at asurface of the fiber web including the perforations. For instance, insome embodiments, the average largest cross-sectional dimension (e.g.,diameter) may be greater than or equal to about 1 mm, greater than orequal to about 2 mm, greater than or equal to about 3 mm, greater thanor equal to about 6 mm, greater than or equal to about 10 mm, greaterthan or equal to about 20 mm, greater than or equal to about 40 mm,greater than or equal to about 60 mm, greater than or equal to about 80mm, or greater than or equal to about 90 mm. In certain embodiments, theaverage largest cross-sectional dimension may be less than or equal toabout 100 mm, less than or equal to about 90 mm, less than or equal toabout 80 mm, less than or equal to about 60 mm, less than or equal toabout 40 mm, less than or equal to about 20 mm, less than or equal toabout 10 mm, less than or equal to about 6 mm, less than or equal toabout 3 mm, or less than or equal to about 2 mm. Combinations of theabove-referenced ranges are also possible (e.g., greater than or equalto about 1 mm and less than or equal to about 100 mm, greater than orequal to about 6 mm and less than or equal to about 60 mm.). Othervalues of average largest cross-sectional dimensions of the perforationsare also possible. Those skilled in the art would be capable ofselecting a suitable method for determining the average largestcross-sectional dimension of the perforations including, for example,taking the average of at least 10 perforation largest cross-sectionaldimensions measured using a handheld micrometer.

The perforations may also be characterized by the surface area coverageof the perforations (e.g., as a percentage of the surface area of thefiber web comprising perforations). In certain embodiments, theperforations may cover a certain percentage of the surface area of alayer (i.e., the combined surface area of the perforations as apercentage of the total area of the layer as measured by its lengthtimes width). For instance, in some embodiments, the perforations maycover greater than or equal to about 0%, greater than or equal to about1%, greater than or equal to about 2%, greater than or equal to about5%, greater than or equal to about 8%, greater than or equal to about10%, greater than or equal to about 15%, greater than or equal to about20%, greater than or equal to about 25%, greater than or equal to about30%, or greater than or equal to about 40% of the surface area of thelayer. In some instances, perforations may cover less than or equal toabout 50%, less than or equal to about 40%, less than or equal to about30%, less than or equal to about 25%, less than or equal to about 20%,less than or equal to about 15%, less than or equal to about 10%, lessthan or equal to about 5%, less than or equal to about 2%, or less thanor equal to about 1% of the surface area of the layer. Combinations ofthe above-referenced ranges are also possible (e.g., greater than orequal to about 0% and less than or equal to about 50%, greater than orequal to about 2% and less than or equal to about 10%). Other ranges ofcoverage are also possible.

In embodiments, the perforations may be arranged such that a definedperiodicity (i.e., distance between the geometric centers of neighboringperforations) and/or pattern exists in the layer. The periodicity may bemeasured in the machine direction and/or in the cross direction. In someembodiments, the perforations may have an average periodicity of greaterthan or equal to about 2 mm, greater than or equal to about 5 mm,greater than or equal to about 10 mm, greater than or equal to about 12mm, greater than or equal to about 15 mm, greater than or equal to about20 mm, or greater than or equal to about 28 mm. In some instances, theperforations may have an average periodicity of less than or equal toabout 30 mm, less than or equal to about 22 mm, less than or equal toabout 18 mm, less than or equal to about 14 mm, less than or equal toabout 10 mm, or less than or equal to about 6 mm. Combinations of theabove-referenced ranges are also possible (e.g., greater than or equalto about 5 mm and less than or equal to about 20 mm). Other values ofaverage periodicity are also possible.

In some embodiments, the periodicity of the perforations may be regularacross the layer. In other embodiments, the periodicity of theperforations may be irregular and/or may vary based on a certainfactors, such as location in the layer or the pattern of theperforations. In certain embodiments, the plurality of perforations maybe arranged to form a pattern (e.g., simple, checkerboard, honeycomb,cubic, hexagonal, polygonal).

In general, any suitable pattern can be used to achieve the desiredproperties. It should be noted, however, that the plurality ofperforations may not have a defined pattern and/or periodicity in someembodiments.

In general the plurality of perforations may be formed by any suitableprocess. For instance, for a dry web, a plurality of perforations may beformed by a thermo-mechanical process (e.g., thermo-dot bonder, needlepunch perforation) or a mechanical process (e.g., puncture orhydro-entangling). For a wet web, for example, a plurality ofperforations may be formed by using a perforating Dandy-roll or byhydro-entangling. In a thermo-dot bonder, a thermo-mechanical elementapplies heat and force to a fiber web to create perforations. Punctureand Dandy roll processes involve the application of mechanical force ona wet layer during drying to make the perforations. Hydro-entanglingmakes perforations in a fiber web through the application ofhydro-mechanical force on a wet or dry layer. In some cases, theapplication of thermal energy (e.g., a laser) can be used to formperforations. Those skilled in the art would be capable of selectingother suitable means for perforating a fiber web based upon theteachings of the specification including, for example, stamping,cutting, and introducing the perforations during production. Other meansare also possible.

In some embodiments, it should be understood that the fiber web need notinclude any perforations.

In some embodiments, the filter element comprises one or more additionallayers (e.g., a support layer). For example, as illustrated in FIG. 5,filter element 104 comprises fiber web 110 wrapped around core 120(e.g., such that the fiber web forms at least two layers around thecore) and an additional layer 130 directly adjacent (e.g., wrappedaround) fiber web 110. In some embodiments, as illustrated in FIG. 5,the additional layer may be wrapped around the fiber web (e.g., an outersurface of the fiber web). In other embodiments, however, the one ormore additional layers may be in contact with, but not wrapped around,the fiber web.

In some embodiments, the one or more additional layers may be disposedbetween the core and the fiber web. For example, as illustrated in FIG.6, filter element 108 comprises additional layer 130 (e.g., a supportlayer) directly adjacent (e.g., wrapped around) core 120. In some suchembodiments, fiber web 110 may be wrapped around additional layer 130.

In some embodiments, the filter element may comprise at least 1, atleast 2, at least 3, at least 4, at least 5, at least 7, at least 9, atleast 10, at least 11, at least 13, at least 15, at least 17, or atleast 19 layers of the support layer wrapped around the fiber web and/orwrapped around the core. In certain embodiments, the filter elementcomprises less than or equal to 20, less than or equal to 19, less thanor equal to 17, less than or equal to 15, less than or equal to 13, lessthan or equal to 13, less than or equal to 11, less than or equal to 10,less than or equal to 9, less than or equal to 7, less than or equal to5, less than or equal to 4, less than or equal to 3, or less than orequal to 2 layers of the support layer wrapped around the fiber weband/or wrapped around the core. Combinations of the above-referencedranges are also possible (e.g., at least 1 layer and less than or equalto 20 layers, at least 2 layers and less than or equal to 13 layers, atleast 2 layers and less than or equal to 4 layers, at least 5 layers andless than or equal to 10 layers). Other ranges are also possible.

In other embodiments, the filter element may comprise at least 1, atleast 2, at least 3, at least 4, at least 5, at least 7, at least 9, atleast 10, at least 11, at least 13, at least 15, at least 17, or atleast 19 layers of the fiber web wrapped around a support layer and/orwrapped around a core. In certain embodiments, the filter elementcomprises less than or equal to 20, less than or equal to 19, less thanor equal to 17, less than or equal to 15, less than or equal to 13, lessthan or equal to 13, less than or equal to 11, less than or equal to 10,less than or equal to 9, less than or equal to 7, less than or equal to5, less than or equal to 4, less than or equal to 3, or less than orequal to 2 layers of the fiber web wrapped around the support layerand/or wrapped around the core. Combinations of the above-referencedranges are also possible (e.g., at least 1 layer and less than or equalto 20 layers, at least 2 layers and less than or equal to 13 layers, atleast 2 layers and less than or equal to 4 layers, at least 5 layers andless than or equal to 10 layers). Other ranges are also possible.

In an alternative embodiment, the filter element does not comprise acore. For example, the fiber web may be, in some embodiments, cast andwrapped around a removable core (e.g., a sieve) such that the filterelement comprises at least two layers of the fiber web wrapped arounditself.

In certain embodiments, one or more additional layers directly adjacentthe fiber web may facilitate the drainage of a fluid (e.g., an oil) fromthe fiber web.

As described herein, in some embodiments, an gas stream comprising thefluid (e.g., comprising an oil, lubricant, and/or cooling agent) isfiltered using a filter media/filter element described herein by passingthe gas stream including the oil, lubricant, and/or cooling agentthrough the fiber web (or through a filter element comprising the fiberweb, optionally wrapped around a core).

In some embodiments, a filter media or filter element described hereinis tailored for filtering a fluid (e.g., oil, lubricant, and/or coolingagent) having a particular surface tension from an gas stream. Forexample, the fiber webs described herein (e.g., having an oil repellencylevel of between 4 to 6) may be well suited for filtration of oils,lubricants, cooling agents or other fluids having a surface tension ofgreater than or equal to 22 mN/m and less than or equal to 33 mN/m at23° C. and 50% RH (or greater than or equal to 23.8 mN/m and less thanor equal to 26.6 mN/m). In some embodiments, the fluid (e.g., the fluidpresent in the gas stream) has a surface tension of greater than orequal to 22 mN/m, greater than or equal to 24 mN/m, greater than orequal to 26 mN/m, greater than or equal to 28 mN/m, greater than orequal to 30 mN/m, or greater than or equal to 32 mN/m as determined at23° C. and 50% RH by the Du Noüy ring method. In certain embodiments,the fluid has a surface tension of less than or equal to 33 mN/m, lessthan or equal to 32 mN/m, less than or equal to 30 mN/m, less than orequal to 28 mN/m, less than or equal to 26 mN/m, or less than or equalto 24 mN/m as determined at 23° C. and 50% RH by the Du Noüy ringmethod. Combinations of the above-referenced ranges are also possible(e.g., greater than or equal to 22 mN/m and less than or equal to 33mN/m). Other surface tensions of the fluid determined at 23° C. and 50%RH are also possible.

In some embodiments, the fluid (e.g., the fluid present in the gasstream to be filtered by the fiber web, filter element, and/or filtermedia) has a surface tension of greater than or equal to 23.8 mN/m,greater than or equal to 24 mN/m, greater than or equal to 24.5 mN/m,greater than or equal to 25 mN/m, greater than or equal to 25.5 mN/m,greater than or equal to 26 mN/m, or greater than or equal to 26.5 mN/mas determined at the filtration temperature by the Du Noüy ring method.In certain embodiments, the fluid has a surface tension of less than orequal to 26.6 mN/m, less than or equal to 26.5 mN/m, less than or equalto 26 mN/m, less than or equal to 25.5 mN/m, less than or equal to 25mN/m, less than or equal to 24.5 mN/m, or less than or equal to 24 mN/mas determined at the filtration temperature by the Du Noüy ring method.Combinations of the above-referenced ranges are also possible (e.g.,greater than or equal to 23.8 mN/m and less than or equal to 26.6 mN/m).Other surface tensions of the fluid determined at the filtrationtemperature are also possible.

The filtration temperature, as used herein, generally refers thetemperature of the gas stream comprising the fluid that is beingfiltered by a filter element, filter media, and/or fiber web describedherein. In some embodiments, the filtration temperature is greater thanor equal to 40° C., greater than or equal to 50° C., greater than orequal to 60° C., greater than or equal to 70° C., greater than or equalto 80° C., greater than or equal to 90° C., greater than or equal to100° C. greater than or equal to 110° C., greater than or equal to 120°C., greater than or equal to 130° C., or greater than or equal to 140°C. In certain embodiments, the filtration temperature is less than orequal to 150° C., less than or equal to 140° C., less than or equal to130° C., less than or equal to 120° C., less than or equal to 110° C.,less than or equal to 100° C., less than or equal to 90° C., less thanor equal to 80° C., less than or equal to 70° C., less than or equal to60° C., or less than or equal to 50° C. Combinations of theabove-referenced ranges are also possible (e.g., greater than or equalto 70° C. and less than or equal to 150° C., greater than or equal to40° C. and less than or equal to 150° C.). Other filtration temperaturesare also possible.

Non-limiting examples of fluids that may be filtered (e.g., coalesced)by the fiber webs (or filter elements comprising the fiber webs)described herein include oils, lubricants, cooling agents, andcombinations thereof. Non-limiting examples of oils/lubricants that maybe filtered (e.g., coalesced) by the fiber webs described herein includealkanes (e.g., n-heptane, n-octane, n-decane, n-dodecane, n-etradecane,n-hexadecane), polyphenyl ethers (e.g., four-ring polyphenyl ethers,five-ring polyphenyl ethers, modified polyphenyl ethers), glycols andderivatives thereof, paraffinic oils, mineral oil (e.g., naphthenicmineral oils, paraffinic mineral oils) fluorosilicones, fluorinatedpolyethers, glycerol, castor oil, and combinations thereof. Thoseskilled in the art would understand based upon the teachings of thisspecification that these examples are not intended to be limiting andthat additional oils, lubricants, cooling agents, and combinationsthereof are also possible. For example, the oils, lubricants, coolingagents, and combinations thereof may include engine oils, liquidcompounds of natural and refined gas, fractions of distillation columnswith liquid and/or gas mixtures, food-based oils, liquid and gas streamsfrom fracking, droplets of mercury and its alloys,polymer/oligomer/monomer droplets (e.g., in the ventilation of chemicalplants), condensed liquid from exhaust systems, or the like. Asdescribed above, in some embodiments, the fluid to be filtered by thefiber webs described herein have a particular surface tension (e.g.,between 22 mN/m and 33 mN/m at 23° C. at 50% RH).

In some embodiments, the fiber web may include glass fibers (e.g.,microglass fibers, chopped strand glass fibers, or a combinationthereof). Microglass fibers and chopped strand glass fibers are known tothose skilled in the art. One skilled in the art is able to determinewhether a glass fiber is microglass or chopped strand by observation(e.g., optical microscopy, electron microscopy). Microglass fibers mayalso have chemical differences from chopped strand glass fibers. In somecases, though not required, chopped strand glass fibers may contain agreater content of calcium or sodium than microglass fibers. Forexample, chopped strand glass fibers may be close to alkali free withhigh calcium oxide and alumina content. Microglass fibers may contain10-15% alkali (e.g., sodium, magnesium oxides) and have relatively lowermelting and processing temperatures. The terms refer to the technique(s)used to manufacture the glass fibers. Such techniques impart the glassfibers with certain characteristics. In general, chopped strand glassfibers are drawn from bushing tips and cut into fibers in a processsimilar to textile production. Chopped strand glass fibers are producedin a more controlled manner than microglass fibers, and as a result,chopped strand glass fibers will generally have less variation in fiberdiameter and length than microglass fibers. Chopped strand diameterstend to follow a normal distribution. Though, it can be appreciated thatchopped strand glass fibers may be provided in any appropriate averagediameter distribution (e.g., Gaussian distribution). Microglass fibersare drawn from bushing tips and further subjected to flame blowing orrotary spinning processes. In some cases, fine microglass fibers may bemade using a remelting process. In this respect, microglass fibers maybe fine or coarse. As used herein, fine microglass fibers are less thanor equal to 1 micron in diameter and coarse microglass fibers aregreater than or equal to 1 micron in diameter.

In some embodiments, the average diameter of the glass fibers may begreater than or equal to about 0.01 microns, greater than or equal toabout 0.1 microns, greater than or equal to about 0.4 microns, greaterthan or equal to about 0.5 microns, greater than or equal to about 1micron, greater than or equal to about 2 microns, greater than or equalto about 5 microns, greater than or equal to about 10 microns, greaterthan or equal to about 15 microns, greater than or equal to about 20microns, greater than or equal to about 30 microns, or greater than orequal to about 40 microns. In some instances, the glass fibers may havean average fiber diameter of less than or equal to about 50 microns,less than or equal to about 40 microns, less than or equal to about 30microns, less than or equal to about 25 microns, less than or equal toabout 20 microns, less than or equal to about 15 microns, less than orequal to about 10 microns, less than or equal to about 5 microns, lessthan or equal to about 2 microns, less than or equal to about 1 micron,less than or equal to about 0.5 microns, less than or equal to about 0.4microns, or less than or equal to about 0.1 microns. Combinations of theabove-referenced ranges are also possible (e.g., greater than or equalto about 0.01 microns and less than or equal to about 50 microns,greater than or equal to about 0.4 microns and less than or equal toabout 10 microns). Other values of average fiber diameter are alsopossible. In some embodiments, glass fibers may have a length in therange of between about 0.05 mm and about 50 mm. In some embodiments, theaverage length of the glass fibers may be less than or equal to about 50mm, less than or equal to about 40 mm, less than or equal to about 30mm, less than or equal to about 25 mm, less than or equal to about 20mm, less than or equal to about 10 mm, less than or equal to about 5 mm,less than or equal to about 1 mm, less than or equal to about 0.5 mm,less than or equal to about 0.3 mm, or less than or equal to about 0.1mm. In certain embodiments, the average length of the glass fibers maybe greater than or equal to about 0.05 mm, greater than or equal toabout 0.1 mm, greater than or equal to about 0.3 mm, greater than orequal to about 0.5 mm, greater than or equal to about 1 mm, greater thanor equal to about 5 mm, greater than or equal to about 10 mm, greaterthan or equal to about 20 mm, greater than or equal to about 25 mm,greater than or equal to about 30 mm, or greater than or equal to about40 mm. Combinations of the above-referenced ranges are also possible(e.g., greater than or equal to about 0.05 mm and less than or equal toabout 50 mm, greater than or equal to about 0.3 mm and less than orequal to about 20 mm). Other values of average length are also possible.

It should be appreciated that the above-noted dimensions are notlimiting and that the microglass and/or chopped strand fibers, as wellas the other fibers described herein, may also have other dimensions.

In some embodiments, the fiber web (and/or one or more additionallayers, such as support layers) in the filter media may includesynthetic fibers. Synthetic fibers may include any suitable type ofsynthetic polymer. Examples of suitable synthetic fibers include staplefibers, polyesters (e.g., polyethylene terephthalate, polybutyleneterephthalate), polycarbonate, polyamides (e.g., various nylonpolymers), polyaramid (e.g., Kevlar®, Nomex®), polyimide, polyphenylenesulfide, polyphenylene oxide, polyethylene, polypropylene, polyetherether ketone, polyolefin, acrylics, polyvinyl alcohol, regeneratedcellulose (e.g., synthetic cellulose such lyocell, rayon),polyacrylonitriles, polyvinylidene fluoride (PVDF), copolymers ofpolyethylene and PVDF, polyether sulfones, halogenated polymers, andcombinations thereof. In some embodiments, the synthetic fibers areorganic polymer fibers. Synthetic fibers may also includemulti-component fibers (i.e., fibers having multiple compositions suchas bicomponent fibers). In some cases, synthetic fibers may includemeltblown, meltspun, melt electrospun, solvent electrospun, orcentrifugal spun fibers, which may be formed of polymers describedherein (e.g., polyester, polypropylene). In other cases, syntheticfibers may be electrospun fibers. The fiber web may also includecombinations of more than one type of synthetic fiber. It should beunderstood that other types of synthetic fiber types may also be used.

In some embodiments, the average diameter of the synthetic fibers in thefiber web may be, for example, greater than or equal to about 0.5microns, greater than or equal to about 0.6 microns, greater than orequal to about 1 micron, greater than or equal to about 2 microns,greater than or equal to about 3 microns, greater than or equal to about4 microns, greater than or equal to about 6 microns, greater than orequal to about 8 microns, greater than or equal to about 10 microns,greater than or equal to about 15 microns, greater than or equal toabout 20 microns, greater than or equal to about 30 microns, or greaterthan or equal to about 40 microns. In some instances, the syntheticfibers may have an average diameter of less than or equal to about 50microns, less than or equal to about 40 microns, less than or equal toabout 30 microns, less than or equal to about 20 microns, less than orequal to about 15 microns, less than or equal to about 10 microns, lessthan or equal to about 8 microns, less than or equal to about 6 microns,less than or equal to about 4 microns, less than or equal to about 3microns, less than or equal to about 2 microns, less than or equal toabout 1 micron, or less than or equal to about 0.6 microns. Combinationsof the above-referenced ranges are also possible (e.g., greater than orequal to about 0.5 micron and less than or equal to about 50 microns,greater than or equal to about 0.6 microns and less than or equal toabout 20 microns). Other values of average fiber diameter are alsopossible.

In some cases, the synthetic fibers in the fiber web may have an averagelength of greater than or equal to about 0.25 mm, greater than or equalto about 0.5 mm, greater than or equal to about 1 mm, greater than orequal to about 2 mm, greater than or equal to about 4 mm, greater thanor equal to about 6 mm, greater than or equal to about 8 mm, greaterthan or equal to about 10 mm, greater than or equal to about 15 mm, orgreater than or equal to about 20 mm. In some instances, syntheticfibers may have an average length of less than or equal to about 30 mm,less than or equal to about 20 mm, less than or equal to about 15 mm,less than or equal to about 10 mm, less than or equal to about 8 mm,less than or equal to about 6 mm, less than or equal to about 4 mm, lessthan or equal to about 2 mm, less than or equal to about 1 mm, or lessthan or equal to about 0.5 mm. Combinations of the above-referencedranges are also possible (e.g., greater than or equal to about 0.25 mmand less than or equal to about 25 mm, greater than or equal to about 3mm and less than or equal to about 15 mm). Other values of average fiberlength are also possible.

In some embodiments, a filter media, filter element, fiber web and/orone or more additional layers described herein may comprise binderfibers (e.g., bicomponent fibers). The binder fibers can be formed, forexample, from any material that is effective to facilitate thermalbonding between the fiber web and the support layer, and will thus havean activation temperature that is lower than the melting temperature ofany non-binder fibers. The binder fibers can be monocomponent fibers orany one of a number of bicomponent binder fibers. In one embodiment, thebinder fibers can be bicomponent fibers, and each component can have adifferent melting temperature. For example, the binder fibers caninclude a core and a sheath where the activation temperature of thesheath is lower than the melting temperature of the core. This allowsthe sheath to melt prior to the core, such that the sheath binds toother fibers in the layer, while the core maintains its structuralintegrity. This may be particularly advantageous in that it creates amore cohesive layer for trapping filtrate. The core/sheath binder fiberscan be concentric or non-concentric, and exemplary core/sheath binderfibers can include the following: a polyester core/copolyester sheath, apolyester core/polyethylene sheath, a polyester core/polypropylenesheath, a polypropylene core/polyethylene sheath, a polyamidecore/polyethylene sheath, and combinations thereof. Other exemplarybicomponent binder fibers can include split fiber fibers, side-by-sidefibers, and/or “island in the sea” fibers. In an exemplary embodiment,the binder fiber comprises polyvinylalcohol (e.g., as a dissolvingfiber). The binder fibers may comprise a thermoplastic polymer. Theaverage diameter of the binder fibers may be, for example, greater thanor equal to about 0.5 microns, greater than or equal to about 0.6microns, greater than or equal to about 1 micron, greater than or equalto about 2 microns, greater than or equal to about 3 microns, greaterthan or equal to about 4 microns, greater than or equal to about 6microns, greater than or equal to about 8 microns, greater than or equalto about 10 microns, greater than or equal to about 15 microns, greaterthan or equal to about 20 microns, greater than or equal to about 30microns, or greater than or equal to about 40 microns. In someinstances, the binder fibers may have an average diameter of less thanor equal to about 50 microns, less than or equal to about 40 microns,less than or equal to about 30 microns, less than or equal to about 20microns, less than or equal to about 15 microns, less than or equal toabout 10 microns, less than or equal to about 8 microns, less than orequal to about 6 microns, less than or equal to about 4 microns, lessthan or equal to about 3 microns, less than or equal to about 2 microns,less than or equal to about 1 micron, or less than or equal to about 0.6microns. Combinations of the above-referenced ranges are also possible(e.g., greater than or equal to about 0.5 micron and less than or equalto about 50 microns, greater than or equal to about 0.6 microns and lessthan or equal to about 20 microns). Other values of average fiberdiameter are also possible.

In some cases, the binder fibers in the fiber web may have an averagelength of greater than or equal to about 0.25 mm, greater than or equalto about 0.5 mm, greater than or equal to about 1 mm, greater than orequal to about 2 mm, greater than or equal to about 4 mm, greater thanor equal to about 6 mm, greater than or equal to about 8 mm, greaterthan or equal to about 10 mm, greater than or equal to about 15 mm, orgreater than or equal to about 20 mm. In some instances, binder fibersmay have an average length of less than or equal to about 30 mm, lessthan or equal to about 20 mm, less than or equal to about 15 mm, lessthan or equal to about 10 mm, less than or equal to about 8 mm, lessthan or equal to about 6 mm, less than or equal to about 4 mm, less thanor equal to about 2 mm, less than or equal to about 1 mm, or less thanor equal to about 0.5 mm. Combinations of the above-referenced rangesare also possible (e.g., greater than or equal to about 0.25 mm and lessthan or equal to about 25 mm, greater than or equal to about 3 mm andless than or equal to about 15 mm). Other values of average fiber lengthare also possible.

The fiber web may comprise a suitable percentage of binder fibers. Forexample, in some embodiments, the weight percentage of binder fiberspresent in the fiber web may be at least about 0 wt %, at least about 2wt %, at least about 5 wt %, at least about 7 wt %, or at least about 10wt %. In certain embodiments, the weight percentage of binder fiberspresent in the fiber web may be less than or equal to about 15 wt %,less than or equal to about 10 wt %, less than or equal to about 7 wt %,less than or equal to about 5 wt %, or less than or equal to about 2 wt%. Combinations of the above-referenced ranges are also possible (e.g.,at least about 0 wt % and less than or equal to about 10 wt %). Otherranges are also possible.

In some embodiments, the fiber web may include one or more cellulosefibers, such as softwood fibers, hardwood fibers, a mixture of hardwoodand softwood fibers, regenerated cellulose fibers, and mechanical pulpfibers (e.g., groundwood, chemically treated mechanical pulps, andthermomechanical pulps). Exemplary softwood fibers include fibersobtained from mercerized southern pine (e.g., mercerized southern pinefibers or “HPZ fibers”), northern bleached softwood kraft (e.g., fibersobtained from Robur Flash (“Robur Flash fibers”)), southern bleachedsoftwood kraft (e.g., fibers obtained from Brunswick pine (“Brunswickpine fibers”)), or chemically treated mechanical pulps (“CTMP fibers”).For example, HPZ fibers can be obtained from Buckeye Technologies, Inc.,Memphis, Tenn.; Robur Flash fibers can be obtained from Rottneros AB,Stockholm, Sweden; and Brunswick pine fibers can be obtained fromGeorgia-Pacific, Atlanta, Ga. Exemplary hardwood fibers include fibersobtained from Eucalyptus (“Eucalyptus fibers”). Eucalyptus fibers arecommercially available from, e.g., (1) Suzano Group, Suzano, Brazil(“Suzano fibers”), (2) Group Portucel Soporcel, Cacia, Portugal (“Caciafibers”), (3) Tembec, Inc., Temiscaming, QC, Canada (“Tarascon fibers”),(4) Kartonimex Intercell, Duesseldorf, Germany, (“Acacia fibers”), (5)Mead-Westvaco, Stamford, Conn. (“Westvaco fibers”), and (6)Georgia-Pacific, Atlanta, Ga. (“Leaf River fibers”).

The average diameter of the cellulose fibers in the fiber web may be,for example, greater than or equal to about 1 micron, greater than orequal to about 2 microns, greater than or equal to about 3 microns,greater than or equal to about 4 microns, greater than or equal to about5 microns, greater than or equal to about 8 microns, greater than orequal to about 10 microns, greater than or equal to about 15 microns,greater than or equal to about 20 microns, greater than or equal toabout 30 microns, or greater than or equal to about 40 microns. In someinstances, the cellulose fibers may have an average diameter of lessthan or equal to about 50 microns, less than or equal to about 40microns, less than or equal to about 30 microns, less than or equal toabout 20 microns, less than or equal to about 15 microns, less than orequal to about 10 microns, less than or equal to about 7 microns, lessthan or equal to about 5 microns, less than or equal to about 4 microns,or less than or equal to about 2 microns. Combinations of theabove-referenced ranges are also possible (e.g., greater than or equalto about 1 micron and less than or equal to about 5 microns). Othervalues of average fiber diameter are also possible.

In some embodiments, the cellulose fibers may have an average length.For instance, in some embodiments, cellulose fibers may have an averagelength of greater than or equal to about 0.5 mm, greater than or equalto about 1 mm, greater than or equal to about 2 mm, greater than orequal to about 3 mm, greater than or equal to about 4 mm, greater thanor equal to about 5 mm, greater than or equal to about 6 mm, or greaterthan or equal to about 8 mm. In some instances, cellulose fibers mayhave an average length of less than or equal to about 10 mm, less thanor equal to about 8 mm, less than or equal to about 6 mm, less than orequal to about 4 mm, less than or equal to about 2 mm, or less than orequal to about 1 mm. Combinations of the above-referenced ranges arealso possible (e.g., greater than or equal to about 1 mm and less thanor equal to about 3 mm). Other values of average fiber length are alsopossible.

In general, the fiber web may include any suitable fiber type. In someembodiments, the fiber web may include more than one type of fiber. Forexample, in certain embodiments, the fiber web may include one or moreof a glass fiber, synthetic fiber, a bicomponent fiber, and/or acellulose fiber (e.g., regenerated, Lyocell, etc.), as described herein.

In some embodiments, the fiber web may include glass fibers (e.g.,microglass and/or chopped glass fibers). For instance, in someembodiments, the weight percentage of the glass fibers in the fiber webmay be, for example, greater than or equal to about 0%, greater than orequal to about 10%, greater than or equal to about 25%, greater than orequal to about 50%, greater than or equal to about 75%, greater than orequal to 80%, greater than or equal to 90%, greater than or equal to95%, greater than or equal to 98%, or greater than or equal to 99%. Insome instances, the weight percentage of the glass fibers in the fiberweb may be less than or equal to about 100%, less than or equal to about75%, less than or equal to about 50%, less than or equal to about 25%,less than or equal to about 5%, or less than or equal to about 2%.Combinations of the above-referenced ranges are also possible (e.g.,greater than or equal to about 0% and less than or equal to about 99%).Other values of weight percentage of the glass in the fiber web are alsopossible. In some embodiments, the fiber web includes 100% glass fibers.

The ratio between the weight percentage of chopped strand glass fibersand microglass fibers provides for different characteristics in thefilter media. In general, increasing the percentage of fine glass fiberswill increase the overall surface area of the filter media; and,increasing the percentage of coarse glass fibers will decrease theoverall surface area of the filter media. Thus, in general, increasingthe amount of chopped strand glass fibers as compared to the amount ofmicroglass fibers decreases the overall surface area of the filtermedia; and, increasing the amount of microglass fibers as compared tothe amount of chopped strand glass fibers increases the surface area ofthe filter media. Increasing the amount of chopped strand glass fiberswithin the filter media also increases the pleatability of the filtermedia (i.e., the ability of a filter to be pleated).

The percentage of chopped strand glass fibers and microglass fibers(e.g., coarse and/or fine) within the filter media are selected toprovide desired characteristics.

Various percentages of chopped strand glass fibers can be includedwithin the glass fibers in the fiber web. In some embodiments, choppedstrand glass fibers may make up less than or equal to about 80% byweight of the glass fiber in the fiber web, less than about 75% byweight of the glass fiber in the fiber web, less than about 50% byweight of the glass fiber in the fiber web, less than about 40% byweight of the glass fiber in the fiber web, less than about 35% byweight of the glass fiber in the fiber web, less than about 25% byweight of the glass fiber in the fiber web, less than about 20% byweight of the glass fiber in the web, or less than about 3% by weight ofthe glass fiber in the fiber web. In certain embodiments, chopped strandglass fibers may make up greater than about 0% by weight of the glassfiber in the fiber web, greater than about 1% by weight of the glassfiber in the fiber web, greater than about 3% by weight of the glassfiber in the fiber web, greater than about 20% by weight of the glassfiber in the fiber web, greater than about 25% by weight of the glassfiber in the fiber web, greater than about 35% by weight of the glassfiber in the fiber web, greater than about 40% by weight of the glassfiber in the fiber web, greater than about 50% by weight of the glassfiber in the fiber web, or greater than 75% by weight of the glass fiberin the fiber web.

Combinations of the above-referenced ranges are also possible (e.g.,between about 1% by weight and about 50% by weight of the glass fibersin the fiber web, between about 3% by weight and about 35% by weight ofthe glass fibers in the fiber web, or between about 3% by weight and 25%by weight of the glass fibers in the fiber web). In certain embodiments,substantially all of the glass fibers in the fiber web are choppedstrand glass fibers.

Additionally, different percentages of microglass fibers are includedwithin the glass fibers within the web. In some embodiments, microglassfibers may make up greater than about 20% by weight of the glass fibersin the fiber web, greater than about 25% by weight of the glass fibersin the fiber web, greater than about 50% by weight of the glass fibersin the fiber web, greater than about 60% by weight of the glass fibersin the fiber web, greater than about 65% by weight of the glass fibersin the fiber web, greater than about 75% by weight of the glass fibersin the fiber web, greater than about 80% by weight of the glass fibersin the fiber web, greater than about 97% by weight of the glass fibersin the fiber web, or greater than about 99% by weight of the glassfibers in the fiber web. In certain embodiments, microglass fibers maymake up less than about 100% by weight of the glass fibers in the fiberweb, less than about 99% by weight of the glass fibers in the fiber web,less than about 97% by weight of the glass fibers in the fiber web, lessthan about 80% by weight of the glass fibers in the fiber web, less thanabout 75% by weight of the glass fibers in the fiber web, less thanabout 65% by weight of the glass fibers in the fiber web, less thanabout 60% by weight of the glass fibers in the fiber web, less thanabout 50% by weight of the glass fibers in the fiber web, less thanabout 25% by weight of the glass fibers in the fiber web, or less thanabout 20% by weight of the glass fibers in the fiber web. Combinationsof the above-referenced ranges are also possible (e.g., between about45% by weight and about 97% by weight of the glass fibers in the fiberweb). Other ranges are also possible.

Coarse microglass fibers, fine microglass fibers, or a combination ofmicroglass fibers thereof may be included within the glass fibers of theweb. For coarse microglass fibers, in some embodiments, coarsemicroglass fibers may make up greater than or equal to about 40%,greater than or equal to about 50%, greater than or equal to about 60%,greater than or equal to about 70%, greater than or equal to about 75%,or greater than or equal to about 80% by weight of the total glassfibers in the fiber web. In certain embodiments, coarse microglassfibers may make up less than about 90%, less than about 80%, less thanabout 75%, less than about 70%, less than about 60%, or less than about50% by weight of the total fibers in the fiber web. Combinations of theabove-referenced ranges are also possible (e.g., between about 40% andabout 90% by weight of the total fibers in the fiber web, between about75% and about 90% by weight of the total fibers in the fiber web, orbetween about 60% and about 70% by weight of the total fibers in thefiber web). Other ranges are also possible.

For fine microglass fibers, in some embodiments, fine microglass fibersmake up greater than or equal to about 0%, greater than or equal toabout 2%, greater than or equal to about 5%, greater than or equal toabout 10%, greater than or equal to about 12%, greater than or equal toabout 15% or greater than or equal to about 20% by weight of the totalfibers in the fiber web. In certain embodiments, fine microglass fibersmake up less than about 25%, less than about 20%, less than about 15%,less than about 12%, less than about 10%, less than about 5%, or lessthan about 2% by weight of the total fibers in the fiber web.Combinations of the above-referenced ranges are also possible (e.g.,between about 0% and about 25% by weight of the totalfibers in the fiberweb, between about 5% and about 10% by weight of the totalfibers in thefiber web, or between about 2% and about 12% by weight of thetotalfibers in the fiber web). Other ranges are also possible.

In some embodiments in which synthetic fibers are included in the fiberweb, the weight percentage of synthetic fibers in the fiber web may begreater than or equal to about 1%, greater than or equal to about 3%,greater than or equal to about 5%, greater than or equal to about 10%,greater than or equal to about 20%, greater than or equal to about 40%,greater than or equal to about 60%, greater than or equal to about 80%,greater than or equal to about 90%, or greater than or equal to about95%. In some instances, the weight percentage of synthetic fibers in thefiber web may be less than or equal to about 100%, less than or equal toabout 98%, less than or equal to about 85%, less than or equal to about75%, less than or equal to about 50%, less than or equal to about 10%,less than or equal to about 5%, less than or equal to about 3%, or lessthan or equal to about 1%. Combinations of the above-referenced rangesare also possible (e.g., greater than or equal to about 1% and less thanor equal to about 100%, greater than or equal to about 80% and less thanor equal to about 100%). Other values of weight percentage of syntheticfibers in the fiber web are also possible. In some embodiments, thefiber web includes 100% synthetic fibers. In other embodiments, thefiber web may include 0% synthetic fibers.

In certain embodiments, the fiber web may optionally include cellulosefibers, such as regenerated cellulose (e.g., rayon, Lyocell),fibrillated synthetic fibers, microfibrillated cellulose, and naturalcellulose fibers (e.g., hardwood, softwood). For instance, in someembodiments, the weight percentage of cellulose fibers in the fiber webmay be greater than or equal to about 1%, greater than or equal to about5%, greater than or equal to about 10%, greater than or equal to about15%, greater than or equal to about 45%, greater than or equal to about65%, or greater than or equal to about 90%. In some instances, theweight percentage of the cellulose fibers in the fiber web may be lessthan or equal to about 100%, less than or equal to about 85%, less thanor equal to about 55%, less than or equal to about 20%, less than orequal to about 10%, or less than or equal to about 2%. Combinations ofthe above-referenced ranges are also possible (e.g., greater than orequal to about 1% and less than or equal to about 100%). Other values ofweight percentage of the cellulose fibers in the fiber web are alsopossible. In some embodiments, the fiber web includes 100% cellulosefibers. In other embodiments, the fiber web may include 0% cellulosefibers.

As noted above, in some embodiments at least one surface of the fiberweb may be modified such that the fiber web has an oil repellency levelof between 4 and 6. In some embodiments, the fiber web may have at leastone modified surface. In some embodiments, the fiber web comprises aplurality of fibers wherein at least a portion of the fibers comprise amodified surface. The material used to modify at least one surface ofthe fiber web and/or fibers may be applied on any suitable portion ofthe fiber web. In some embodiments, the material may be applied suchthat one or more surfaces of the fiber web are modified withoutsubstantially modifying the interior of the fiber web. In someinstances, a single surface of the fiber web may be modified. Forexample, the upstream surface of the fiber web may be coated. In otherinstances, more than one surface of the fiber web may be coated (e.g.,the upstream and downstream surfaces). In other embodiments, at least aportion of the interior of the fiber web may be modified along with atleast one surface of the fiber web. In some embodiments, the entirefiber web is modified with the material.

In general, any suitable method for modifying the surface chemistry ofat least one surface of the fiber web and/or the plurality of fibers maybe used. In some embodiments, the surface chemistry of the fiber weband/or the plurality of fibers may be modified by coating at least aportion of the surface, using melt-additives, and/or altering theroughness of the surface.

In some embodiments, the surface modification may be a coating. Incertain embodiments, a coating process involves introducing resin or amaterial (e.g., hydrophobic material, hydrophilic material, lipophilicmaterial, lipophobic material) dispersed in a solvent or solvent mixtureinto a pre-formed fiber layer (e.g., a pre-formed fiber web formed by ameltblown process). Non-limiting examples of coating methods include theuse of chemical vapor deposition, a slot die coater, gravure coating,screen coating, size press coating (e.g., a two roll-type or a meteringblade type size press coater), film press coating, blade coating,roll-blade coating, air knife coating, roll coating, foam application,reverse roll coating, bar coating, curtain coating, champlex coating,brush coating, Bill-blade coating, short dwell-blade coating, lipcoating, gate roll coating, gate roll size press coating, laboratorysize press coating, melt coating, dip coating, knife roll coating, spincoating, spray coating, gapped roll coating, roll transfer coating,padding saturant coating, and saturation impregnation. Other coatingmethods are also possible. In some embodiments, the hydrophilic,hydrophobic, lipophilic, and/or lipophobic material may be applied tothe fiber web using a non-compressive coating technique. Thenon-compressive coating technique may coat the fiber web, while notsubstantially decreasing the thickness of the web. In other embodiments,the resin may be applied to the fiber web using a compressive coatingtechnique.

In one set of embodiments, a surface described herein is modified usingchemical vapor deposition. In chemical vapor deposition, the fiber webis exposed to gaseous reactants from gas or liquid vapor that aredeposited onto the fiber web under high energy level excitation such asthermal, microwave, UV, electron beam or plasma. Optionally, a carriergas such as oxygen, helium, argon and/or nitrogen may be used.

Other vapor deposition methods include atmospheric pressure chemicalvapor deposition (APCVD), low pressure chemical vapor deposition(LPCVD), metal-organic chemical vapor deposition (MOCVD), plasmaassisted chemical vapor deposition (PACVD) or plasma enhanced chemicalvapor deposition (PECVD), laser chemical vapor deposition (LCVD),photochemical vapor deposition (PCVD), chemical vapor infiltration (CVI)and chemical beam epitaxy (CBE).

In physical vapor deposition (PVD) thin films are deposited by thecondensation of a vaporized form of the desired film material ontosubstrate. This method involves physical processes such ashigh-temperature vacuum evaporation with subsequent condensation, orplasma sputter bombardment rather than a chemical reaction.

After applying the coating to the fiber web, the coating may be dried byany suitable method. Non-limiting examples of drying methods include theuse of a photo dryer, infrared dryer, hot air oven steam-heatedcylinder, or any suitable type of dryer familiar to those of ordinaryskill in the art.

In some embodiments, at least a portion of the fibers of the fiber webmay be coated without substantially blocking the pores of the fiber web.In some instances, substantially all of the fibers may be coated withoutsubstantially blocking the pores. In some embodiments, the fiber web maybe coated with a relatively high weight percentage of resin or materialwithout blocking the pores of the fiber web using the methods describedherein (e.g., by dissolving and/or suspending one or more material in asolvent to form the resin).

In some embodiments, the surface may be modified using melt additives.Melt-additives are functional chemicals that are added to thermoplasticsfibers during an extrusion process that may render different physicaland chemical properties at the surface from those of the thermoplasticitself after formation.

In some embodiments, the material may undergo a chemical reaction (e.g.,polymerization) after being applied to the fiber web. For example, asurface of the fiber web may be coated with one or more monomers thatcan be polymerized after coating. In another example, a surface of thefiber web may include monomers, as a result of the melt additive, thatare polymerized after formation of the fiber web. In some suchembodiments, an in-line polymerization may be used. In-linepolymerization (e.g., in-line ultraviolet polymerization) is a processto cure a monomer or liquid polymer solution onto a substrate underconditions sufficient to induce polymerization (e.g., under UVirradiation).

In general, any suitable material may be used to alter the surfacechemistry, and accordingly the lipophilicity, of the fiber web. In someembodiments, the material may be charged. In some such embodiments, asdescribed in more detail herein, the surface charge of the fiber web mayfurther facilitate coalescence and/or increase the oil carry over. Forinstance, in certain embodiments, a fiber web having a lipophilicmodified surface may have a decreased oil carry over and/or producelarger coalesced droplets than a fiber web having a non-modifiedsurface.

In general, the net charge of the modified surface may be negative,positive, or neutral. In some instances, the modified surface maycomprise a negatively charged material and/or a positively chargedmaterial. In some embodiments, the surface may be modified with anelectrostatically neutral material. Non-limiting examples of materialsthat may be used to modify the surface include polyelectrolytes (e.g.,anionic, cationic), oligomers, polymers (e.g., fluorinated polymers,perfluoroalkyl ethyl methacrylate, polycaprolactone, poly[bis(trifluoroethoxy)phosphazene], small molecules (e.g., carboxylatecontaining monomers, amine containing monomers, polyol), ionic liquids,monomer precursors, and gases, and combinations thereof.

In embodiments in which fluorinated polymers are included, the polymermay include a species having the formula —C_(n)F_(2n+1) or —C_(n)F_(m),where n is an integer greater than 1, and m is an integer greater than 1(e.g., —C₆F₁₃). In some embodiments, anionic polyelectrolytes may beused to modify the surface of the fiber web. For example, one or moreanionic polyelectrolytes may be spray or dip coated onto at least onesurface of the fiber web. In some embodiments, cationic polyelectrolytesmay be used to modify the surface of the fiber web. In some embodiments,silicone (or derivatives thereof) may be used to modify the surface ofthe fiber web. For example, in certain embodiments, at least a surfaceof the fiber web may be treated or coated with polydimethylsiloxane. Incertain embodiments, the surface of the fiber web may be silylated(e.g., a substituted silyl group may be incorporated onto at least asurface of the fiber web).

In certain embodiments, a filler material (e.g., an organic fillermaterial, and inorganic filler material) may be added to the fiber webto modify the surface and/or oil repellency level of the fiber web. Insome embodiments, small molecules (e.g., monomers, polyol) may be usedto modify the oil repellency level of the fiber webIn certainembodiments, small molecules may be used as melt-additives. In anotherexample, small molecules may be deposited on at least one surface of thefiber web via coating (e.g., chemical vapor deposition). Regardless ofthe modification method, the small molecules on a surface of the fiberweb may be polymerized after deposition in some embodiments.

In certain embodiments, the small molecules, such as monobasiccarboxylic acids and/or unsaturated dicarboxylic (dibasic) acids, may beused to modify at least one surface of the fiber web. In certainembodiments, the small molecules may be amine containing smallmolecules. The amine containing small molecules may be primary,secondary, or tertiary amines. In some such cases, the amine containingsmall molecule may be a monomer. In some embodiments, the small moleculemay be an inorganic or organic hydrophobic molecule. Non-limitingexamples include hydrocarbons (e.g., CH₄, C₂H₂, C₂H₄, C₆H₆),fluorocarbons (e.g., CF₄, C₂F₄, C₃F₆, C₃F₈, C₄H₈, C₅H₁₂, C₆F₆, C₆F₁₃, orother fluorocarbons having the formula —C_(n)F_(2n+1) or —C_(n)F_(m),where n is an integer greater than 1, and m is an integer greater than1), silanes (e.g., SiH₄, Si₂H₆, Si₃H₈, Si₄H₁₀), organosilanes (e.g.,methylsilane, dimethylsilane, triethylsilane), and siloxanes (e.g.,dimethylsiloxane, hexamethyldisiloxane). In certain embodiments,suitable hydrocarbons for modifying a surface of the fiber web may havethe formula C_(x)H_(y), where x is an integer from 1 to 10 and y is aninteger from 2 to 22. In certain embodiments, suitable silanes formodifying a surface of the fiber web may have the formula Si_(n)H_(2n+2)where any hydrogen may be substituted for a halogen (e.g., Cl , F, Br,I), where n is an integer from 1 to 10.

As used herein, “small molecules” refers to molecules, whethernaturally-occurring or artificially created (e.g., via chemicalsynthesis) that have a relatively low molecular weight. Typically, asmall molecule is an organic compound (i.e., it contains carbon). Thesmall organic molecule may contain multiple carbon-carbon bonds,stereocenters, and other functional groups (e.g., amines, hydroxyl,carbonyls, and heterocyclic rings, etc.). In certain embodiments, themolecular weight of a small molecule is at most about 1,000 g/mol, atmost about 900 g/mol, at most about 800 g/mol, at most about 700 g/mol,at most about 600 g/mol, at most about 500 g/mol, at most about 400g/mol, at most about 300 g/mol, at most about 200 g/mol, or at mostabout 100 g/mol. In certain embodiments, the molecular weight of a smallmolecule is at least about 100 g/mol, at least about 200 g/mol, at leastabout 300 g/mol, at least about 400 g/mol, at least about 500 g/mol, atleast about 600 g/mol, at least about 700 g/mol, at least about 800g/mol, or at least about 900 g/mol, or at least about 1,000 g/mol.Combinations of the above ranges (e.g., at least about 200 g/mol and atmost about 500 g/mol) are also possible.

In some embodiments, polymers may be used to modify at least one surfaceof the fiber web. For example, one or more polymer may be applied to atleast a portion of a surface of the fiber web via a coating technique.In certain embodiments, the polymer may be formed from monobasiccarboxylic acids and/or unsaturated dicarboxylic (dibasic) acids. Incertain embodiments, the polymer may be a graft copolymer and may beformed by grafting polymers or oligomers to polymers in the fibersand/or fiber web (e.g., resin polymer). The graft polymer or oligomermay comprise carboxyl moieties that can be used to form a chemical bondbetween the graft and polymers in the fibers and/or fiber web.Non-limiting examples of polymers in the fibers and/or fiber web thatcan be used to form a graft copolymer include polyethylene,polypropylene, polycarbonate, polyvinyl chloride,polytetrafluoroethylene, polystyrene, cellulose, polyethyleneterephthalate, polybutylene terephthalate, and nylon, and combinationsthereof. Graft polymerization can be initiated through chemical and/orradiochemical (e.g., electron beam, plasma, corona discharge,UV-irradiation) methods. In some embodiments, the polymer may be apolymer having a repeat unit that comprises an amine (e.g.,polyallylamine, polyethyleneimine, polyoxazoline). In certainembodiments, the polymer may be a polyol.

In some embodiments, a gas may be used to modify at least one surface ofthe fiber web. In some such cases, the molecules in the gas may reactwith material (e.g., fibers, resin, additives) on the surface of thefiber web to form functional groups, such as charged moieties, and/or toincrease the oxygen content on the surface of the fiber web. The weightpercent of the material used to modify at least one surface of the fiberweb may be greater than or equal to about 0.0001 wt %, greater than orequal to about 0.0005 wt %, greater than or equal to about 0.001 wt %,greater than or equal to about 0.005 wt %, greater than or equal toabout 0.01 wt %, greater than or equal to about 0.05 wt %, greater thanor equal to about 0.1 wt %, greater than or equal to about 0.5 wt %,greater than or equal to about 1 wt %, greater than or equal to about 2wt %, or greater than or equal to about 3 wt % of the fiber web. In somecases, the weight percentage of the material used to modify at least onesurface of the fiber web may be less than or equal to about 4 wt %, lessthan or equal to about 3 wt %, less than or equal to about 1 wt %, lessthan or equal to about 0.5 wt %, less than or equal to about 0.1 wt %,less than or equal to about 0.05 wt %, less than or equal to about 0.01wt %, or less than or equal to about 0.005 wt % of the fiber web.Combinations of the above-referenced ranges are also possible (e.g., aweight percentage of material of greater than or equal to about 0.0001wt % and less than about 4 wt %, or greater than or equal to about 0.01wt % and less than about 0.5 wt %). Other ranges are also possible. Theweight percentage of material in the fiber web is based on the drysolids of the fiber web and can be determined by weighing the fiber webbefore and after the material is applied.

The fiber web, as described herein, may have certain structuralcharacteristics such as basis weight. For instance, in some embodiments,the fiber web may have a basis weight of greater than or equal to about1 g/m², greater than or equal to about 5 g/m², greater than or equal toabout 10 g/m², greater than or equal to about 20 g/m², greater than orequal to about 27 g/m², greater than or equal to about 30 g/m², greaterthan or equal to about 40 g/m², greater than or equal to about 50 g/m²,greater than or equal to about 100 g/m², greater than or equal to about150 g/m², greater than or equal to about 200 g/m², greater than or equalto about 250 g/m², greater than or equal to about 270 g/m², greater thanor equal to about 300 g/m², greater than or equal to about 350 g/m²,greater than or equal to about 400 g/m², or greater than or equal toabout 450 g/m². In certain embodiments, the fiber web may have basisweight of less than or equal to about 500 g/m², less than or equal toabout 450 g/m², less than or equal to about 400 g/m², less than or equalto about 350 g/m², less than or equal to about 300 g/m², less than orequal to about 270 g/m², less than or equal to about 250 g/m², less thanor equal to about 200 g/m², less than or equal to about 150 g/m², lessthan or equal to about 100 g/m², less than or equal to about 50 g/m²,less than or equal to about 40 g/m², less than or equal to about 30g/m², less than or equal to about 27 g/m², less than or equal to about25 g/m², less than or equal to about 20 g/m², less than or equal toabout 10 g/m², or less than or equal to about 5 g/m². Combinations ofthe above-referenced ranges are also possible (e.g., greater than orequal to about 1 g/m² and less than or equal to about 500 g/m², greaterthan or equal to about 20 g/m² and less than or equal to about 500 g/m²,greater than or equal to about 27 g/m² and less than or equal to about270 g/m²). Other values of basis weight are also possible. The basisweight may be determined according to the standard ASTM D-846.

The mean flow pore size may be selected as desired. With respect to themean flow pore size of a fiber web, whether the fiber web includesperforations or does not include any perforations, the mean flow poresize as used herein is measured in an area of the fiber web that doesnot include any perforations. In some embodiments, the fiber web mayhave a mean flow pore size of greater than or equal to about 1 microns,greater than or equal to about 3 microns, greater than or equal to about4 microns, greater than or equal to about 5 microns, greater than orequal to about 6 microns, greater than or equal to about 7 microns, orgreater than or equal to about 9 microns. In some instances, the fiberweb may have a mean flow pore size of less than or equal to about 10microns, less than or equal to about 8 microns, less than or equal toabout 6 microns, less than or equal to about 5 microns, less than orequal to about 4 microns, or less than or equal to about 2 microns.Combinations of the above-referenced ranges are also possible (e.g.,greater than or equal to about 3 microns and less than or equal to about6 microns).

Other values of mean flow pore size are also possible. The mean flowpore size may be determined according to the standard ASTM E1294 (2008)(M.F.P.).

The thickness of the fiber web may be selected as desired. For instance,in some embodiments, the fiber web may have a thickness of greater thanor equal to about 0.1 mm, greater than or equal to about 0.2 mm, greaterthan or equal to about 0.3 mm, greater than or equal to about 0.4 mm,greater than or equal to about 0.5 mm, greater than or equal to about1.0 mm, or greater than or equal to about 1.5 mm. In some instances, thefiber web may have a thickness of less than or equal to about 2.0 mm,less than or equal to about 1.2 mm, less than or equal to about 0.5 mm,less than or equal to about 0.4 mm, less than or equal to about 0.3 mm,or less than or equal to about 0.2 mm. Combinations of theabove-referenced ranges are also possible (e.g., a thickness of greaterthan or equal to about 0.2 mm and less than or equal to about 0.5 mm).Other values of thickness are also possible. The thickness may bedetermined according to the standard TAPPI T411.

The fiber web (or filter media) described herein may be used for thefiltration of various particle sizes. In a typical test for measuringefficiency of a layer or the entire media (e.g., according to thestandard ISO 19438), particle counts (particles per milliliter) at theparticle size, x, selected (e.g., where x is 1, 3, 4, 5, 7, 10, 15, 20,25, or 30 microns) upstream and downstream of the layer or media can betaken at ten points equally divided over the time of the test.Generally, a particle size of x means that x micron or greater particleswill be captured by the layer or media. The average of upstream anddownstream particle counts can be taken at the selected particle size.From the average particle count upstream (injected −C₀) and the averageparticle count downstream (passed thru −C) the filtration efficiencytest value for the particle size selected can be determined by therelationship [(1[C/C₀])*100%]. As described herein, efficiency can bemeasured according to standard ISO 19348. A similar protocol can be usedfor measuring initial efficiency, which refers to the efficiencymeasurements of the media at 4 minutes after running the test. Unlessotherwise indicated, efficiency and initial efficiency measurementsdescribed herein refer to values where x =4 microns.

The fiber web (or filter media) may have a relatively high initialefficiency. The initial efficiency of the fiber web may be greater thanor equal to about 1%, greater than or equal to about 5%, greater than orequal to about 10%, greater than or equal to about 20%, greater than orequal to about 30%, greater than or equal to about 40%, greater than orequal to about 50%, greater than or equal to about 60%, greater than orequal to about 70%, greater than or equal to about 80%, greater than orequal to about 90%, greater than or equal to about 95%, greater than orequal to about 96%, greater than or equal to about 97%, greater than orequal to about 98%, greater than or equal to about 99%, or greater thanor equal to about 99.9%. In some instances, the initial efficiency ofthe fiber web may be less than or equal to about 99.99%, less than orequal to about 98%, less than or equal to about 97%, less than or equalto about 96%, less than or equal to about 90%, less than or equal toabout 80%, less than or equal to about 70%, less than or equal to about60%, less than or equal to about 50%, less than or equal to about 40%,less than or equal to about 30%, less than or equal to about 20%, lessthan or equal to about 10%, or less than or equal to about 5%.Combinations of the above-referenced ranges are also possible (e.g.,greater than or equal to about 1% and less than or equal to about99.99%, greater than or equal to about 80% and less than or equal toabout 99.99%). Other values of the initial efficiency of the fiber webare also possible.

The air permeability of the fiber web described herein can vary. In someembodiments, the permeability of the fiber web may be, for example,greater than or equal to about 5 L/m²s, greater than or equal to about10 L/m²s, greater than or equal to about 15 L/m²s, greater than or equalto about 25 L/m²s, greater than or equal to about 50 L/m²s, greater thanor equal to about 100 L/m²s, greater than or equal to about 150 L/m²s,greater than or equal to about 200 L/m²s, greater than or equal to about250 L/m²s, greater than or equal to about 300 L/m²s, greater than orequal to about 500 L/m²s, greater than or equal to about 1000 L/m²s,greater than or equal to about 1500 L/m²s, greater than or equal toabout 1700 L/m²s, greater than or equal to about 2000 L/m²s, or greaterthan or equal to about 2500 L/m²s. In some instances, the airpermeability may be, for example, less than or equal to about 3000L/m²s, less than or equal to about 2500 L/m²s, less than or equal toabout 2000 L/m²s, less than or equal to about 1700 L/m²s, less than orequal to about 1500 L/m²s, less than or equal to about 1000 L/m²s, lessthan or equal to about 500 L/m²s, less than or equal to about 300 L/m²s,less than or equal to about 250 L/m²s, less than or equal to about 200L/m²s, less than or equal to about 150 L/m²s, less than or equal toabout 100 L/m²s, less than or equal to about 50 L/m²s, less than orequal to about 25 L/m²s, less than or equal to about 20 L/m²s, less thanor equal to about 15 L/m²s, or less than or equal to about 10 L/m²s.Combinations of the above-referenced ranges are also possible (greaterthan or equal to about 5 L/m²s and less than or equal to about 3000L/m²s, greater than or equal to about 15 L/m²s and less than or equal toabout 1700 L/m²s). Other ranges of air permeability are also possible.As determined herein, the air permeability is measured according tostandard TAPPI T251 (wherein the flow is 10,000 L/m²/s on 20 cm² area).The permeability of a fiber web is an inverse function of flowresistance and can be measured with a Frazier Permeability Tester. TheFrazier Permeability Tester measures the volume of air per unit of timethat passes through a unit area of media at a fixed differentialpressure across the media.

The overall pressure drop of the fiber web may be selected as desired.For instance, in some embodiments, the fiber web may have an overallpressure drop of less than or equal to about 1700 Pa, less than or equalto about 1500 Pa, less than or equal to about 1000 Pa, less than orequal to about 700 Pa, less than or equal to about 500 Pa, less than orequal to about 250 Pa, less than or equal to about 100 Pa, less than orequal to about 50 Pa, less than or equal to about 25 Pa, less than orequal to about 10 Pa, or less than or equal to about 5 Pa. In certainembodiments, the fiber web may have an overall pressure drop of greaterthan or equal to about 3 Pa, greater than or equal to about 5 Pa,greater than or equal to about 10 Pa, greater than or equal to about 25Pa, greater than or equal to about 50 Pa, greater than or equal to about100 Pa, greater than or equal to about 250 Pa, greater than or equal toabout 500 Pa, greater than or equal to about 700 Pa, greater than orequal to about 1000 Pa, or greater than or equal to about 1500 Pa.Combinations of the above-referenced ranges are also possible (e.g.,greater than or equal to about 3 Pa and less than or equal to about 1700Pa, greater than or equal to about 10 Pa and less than or equal to about700 Pa). Other values of pressure drop are also possible. The pressuredrop may be measured using the TAPPI T251 standard.

As described herein, in some embodiments a filter element comprises acore. In some embodiments, the core may comprise a plastic and/ormetallic net, and/or a mesh. Non-limiting examples of suitable meshesinclude polymer meshes (e.g., comprising fluoropolymers, polyamides,polyolefins, polyesters, polysulfones, polyvinyls, or combinationsthereof) and metal meshes (e.g., comprising stainless steel). In someembodiments, the core comprises a metal sheet (e.g., stainless steel)which may or may not be perforated. In certain embodiments, the core isfibrous. For example, in some embodiments, the core comprises aplurality of synthetic fibers. In some cases, the core may have aspecific weight percentage of synthetic fibers.

For instance, in some embodiments, the weight percentage of syntheticfibers in the core may be greater than or equal to about 0%, greaterthan or equal to about 10%, greater than or equal to about 20%, greaterthan or equal to about 30%, greater than or equal to about 40%, greaterthan or equal to about 55%, greater than or equal to about 70%, greaterthan or equal to about 75%, greater than or equal to about 80%, orgreater than or equal to about 90%. In some instances, the weightpercentage of synthetic fibers in the core may be less than or equal toabout 100%, less than or equal to about 85%, less than or equal to about75%, less than or equal to about 65%, less than or equal to about 55%,less than or equal to about 45%, less than or equal to about 35%, lessthan or equal to about 25%, or less than or equal to about 15%.Combinations of the above-referenced ranges are also possible (e.g.,greater than or equal to about 0% and less than or equal to about 100%).In some embodiments, 100% of the fibers in the core are syntheticfibers. Other values of weight percentage of the synthetic fibers in thecore are also possible.

In some embodiments, the fibers (e.g., synthetic fibers) in the core mayhave an average diameter of greater than or equal to about 0.5 microns,greater than or equal to about 0.6 microns, greater than or equal toabout 1 micron, greater than or equal to about 2 microns, greater thanor equal to about 3 microns, greater than or equal to about 4 microns,greater than or equal to about 6 microns, greater than or equal to about8 microns, greater than or equal to about 10 microns, greater than orequal to about 15 microns, greater than or equal to about 20 microns,greater than or equal to about 30 microns, or greater than or equal toabout 40 microns. In some instances, the fibers in the core may have anaverage diameter of less than or equal to about 50 microns, less than orequal to about 40 microns, less than or equal to about 30 microns, lessthan or equal to about 20 microns, less than or equal to about 15microns, less than or equal to about 10 microns, less than or equal toabout 8 microns, less than or equal to about 6 microns, less than orequal to about 4 microns, less than or equal to about 3 microns, lessthan or equal to about 2 microns, less than or equal to about 1 micron,or less than or equal to about 0.6 microns. Combinations of theabove-referenced ranges are also possible (e.g., greater than or equalto about 0.5 micron and less than or equal to about 50 microns, greaterthan or equal to about 0.6 microns and less than or equal to about 20microns). Other values of average fiber diameter are also possible.

In some embodiments, fibers (e.g., synthetic fibers) in the core mayhave an average length of greater than or equal to about 1 mm, greaterthan or equal to about 2 mm, greater than or equal to about 3 mm,greater than or equal to about 4 mm, greater than or equal to about 6mm, greater than or equal to about 8 mm, greater than or equal to about10 mm, greater than or equal to about 12 mm, greater than or equal toabout 15 mm, greater than or equal to about 20 mm, greater than or equalto about 25 mm, greater than or equal to 30 mm, or greater than or equalto 40 mm. In some instances, the fibers may have an average length ofless than or equal to about 50 mm, less than or equal to about 40 mm,less than or equal to about 30 mm, less than or equal to about 25 mm,less than or equal to about 20 mm, less than or equal to about 15 mm,less than or equal to about 12 mm, less than or equal to about 10 mm,less than or equal to about 8 mm less than or equal to about 7 mm, lessthan or equal to about 5 mm, less than or equal to about 3 mm, less thanor equal to about 2 mm, or less than or equal to about 1.5 mm.Combinations of the above-referenced ranges are also possible (e.g.,greater than or equal to about 1 mm and less than or equal to about 50mm, greater than or equal to about 1 mm and less than or equal to about15 mm, greater than or equal to about 1.5 mm and less than or equal toabout 30 mm,). Other values of average fiber length are also possible.

The core, as described herein, may have certain structuralcharacteristics, such as basis weight, and thickness. For instance, insome embodiments, the core may have a basis weight of greater than orequal to about 3 g/m², greater than or equal to about 10 g/m², greaterthan or equal to about 22 g/m², greater than or equal to about 25 g/m²,greater than or equal to about 30 g/m², greater than or equal to about33 g/m², greater than or equal to about 40 g/m², greater than or equalto about 50 g/m², greater than or equal to about 60 g/m², greater thanor equal to about 70 g/m², greater than or equal to about 80 g/m²,greater than or equal to about 100 g/m², greater than or equal to about200 g/m², greater than or equal to about 300 g/m², or greater than orequal to about 400 g/m². In some instances, the core may have a basisweight of less than or equal to about 500 g/m², less than or equal toabout 400 g/m², less than or equal to about 300 g/m², less than or equalto about 200 g/m², less than or equal to about 100 g/m², less than orequal to about 90 g/m², less than or equal to about 80 g/m², less thanor equal to about 70 g/m², less than or equal to about 60 g/m², lessthan or equal to about 50 g/m², less than or equal to about 40 g/m²,less than or equal to about 33 g/m², less than or equal to about 30g/m², or less than or equal to about 25 g/m². Combinations of theabove-referenced ranges are also possible (e.g., a basis weight ofgreater than or equal to about 22 g/m² and less than or equal to about90 g/m², a basis weight of greater than or equal to about 33 g/m² andless than or equal to about 70 g/m², a basis weight of greater than orequal to about 3 g/m² and less than or equal to about 500 g/m²). Othervalues of basis weight are also possible. The basis weight may bedetermined according to the standard ASTM D-846.

The thickness of the core may be selected as desired. For instance, insome embodiments, the core may have a thickness of greater than or equalto about 0.01 mm, greater than or equal to about 0.1 mm, greater than orequal to about 0.2 mm, greater than or equal to about 0.3 mm, greaterthan or equal to about 0.4 mm, greater than or equal to about 0.5 mm,greater than or equal to about 1.0 mm, greater than or equal to about1.5 mm, greater than or equal to about 2 mm, greater than or equal toabout 3 mm, or greater than or equal to about 4 mm. In some instances,the core may have a thickness of less than or equal to about 5 mm, lessthan or equal to about 4 mm, less than or equal to about 3 mm, less thanor equal to about 2 mm, less than or equal to about 1.2 mm, less than orequal to about 0.5 mm, less than or equal to about 0.4 mm, less than orequal to about 0.3 mm, less than or equal to about 0.2 mm, or less thanor equal to about 0.1 mm. Combinations of the above-referenced rangesare also possible (e.g., a thickness of greater than or equal to about0.01 mm and less than or equal to about 5 mm, a thickness of greaterthan or equal to about 0.1 mm and less than or equal to about 2 mm).Other values of thickness are also possible. The thickness may bedetermined according to the standard TAPPI T411.

As described herein, in some embodiments a filter media may include oneor more support layers. The support layer(s) may include a plurality offibers. In general, a number of different materials can be used to formthe fibers as described below. In some embodiments, the fibers are madefrom cellulose. Examples of cellulose fibers are provided above. Incertain embodiments, the support layer may include synthetic fibers, asdescribed above. In some cases, the support layer may be a perforatedfilm comprising bio-derived and/or metal materials.

In some cases, the support layer may have a specific weight percentageof synthetic fibers. For instance, in some embodiments, the weightpercentage of synthetic fibers in the support layer may be greater thanor equal to about 0%, greater than or equal to about 10%, greater thanor equal to about 20%, greater than or equal to about 30%, greater thanor equal to about 40%, greater than or equal to about 55%, greater thanor equal to about 70%, greater than or equal to about 75%, greater thanor equal to about 80%, or greater than or equal to about 90%. In someinstances, the weight percentage of synthetic fibers in the supportlayer may be less than or equal to about 100%, less than or equal toabout 85%, less than or equal to about 75%, less than or equal to about65%, less than or equal to about 55%, less than or equal to about 45%,less than or equal to about 35%, less than or equal to about 25%, orless than or equal to about 15%. Combinations of the above-referencedranges are also possible (e.g., greater than or equal to about 0% andless than or equal to about 100%). In some embodiments, 100% of thefibers in the support layer are synthetic fibers. Other values of weightpercentage of the synthetic fibers in the support layer are alsopossible.

The support layer may include one or more of glass fibers, cellulosefibers, and/or bicomponent fibers, as described above in the context ofthe fiber web. For instance, in some embodiments, the weight percentageof each of glass fibers, binder fibers, and/or cellulose fibers in thesupport layer may independently be greater than or equal to about 0%,greater than or equal to about 0.1%, greater than or equal to about 1%,greater than or equal to about 2%, greater than or equal to about 5%,greater than or equal to about 10%, greater than or equal to about 15%,greater than or equal to about 20%, greater than or equal to about 30%,greater than or equal to about 40%, greater than or equal to about 50%,greater than or equal to about 60%, greater than or equal to about 70%,greater than or equal to about 80%, or greater than or equal to about90%. In some instances, the weight percentage of each of the glassfibers, binder fibers, and/or cellulose fibers in the support layer mayindependently be less than or equal to about 100%, less than or equal toabout 90%, less than or equal to about 80%, less than or equal to about70%, less than or equal to about 60%, less than or equal to about 50%,less than or equal to about 40%, less than or equal to about 30%, lessthan or equal to about 20%, less than or equal to about 15%, less thanor equal to about 10%, less than or equal to about 5%, less than orequal to about 2%, less than or equal to about 0.5%, or less than orequal to about 0.1%. Combinations of the above-referenced ranges arealso possible (e.g., greater than or equal to about 0% and less than orequal to about 20%). Other values of weight percentages of the fibers inthe support layer are also possible. Examples of glass fibers, andbinder fibers are provided in more detail herein.

In some embodiments, the fibers in the support layer may have an averagediameter of greater than or equal to about 0.5 microns, greater than orequal to about 0.6 microns, greater than or equal to about 1 micron,greater than or equal to about 2 microns, greater than or equal to about3 microns, greater than or equal to about 4 microns, greater than orequal to about 6 microns, greater than or equal to about 8 microns,greater than or equal to about 10 microns, greater than or equal toabout 15 microns, greater than or equal to about 20 microns, greaterthan or equal to about 30 microns, or greater than or equal to about 40microns. In some instances, the fibers in the support layer may have anaverage diameter of less than or equal to about 50 microns, less than orequal to about 40 microns, less than or equal to about 30 microns, lessthan or equal to about 20 microns, less than or equal to about 15microns, less than or equal to about 10 microns, less than or equal toabout 8 microns, less than or equal to about 6 microns, less than orequal to about 4 microns, less than or equal to about 3 microns, lessthan or equal to about 2 microns, less than or equal to about 1 micron,or less than or equal to about 0.6 microns. Combinations of theabove-referenced ranges are also possible (e.g., greater than or equalto about 0.5 micron and less than or equal to about 50 microns, greaterthan or equal to about 0.6 microns and less than or equal to about 20microns). Other values of average fiber diameter are also possible.

In some embodiments, fibers in the support layer may have an averagelength of greater than or equal to about 1 mm, greater than or equal toabout 2 mm, greater than or equal to about 3 mm, greater than or equalto about 4 mm, greater than or equal to about 6 mm, greater than orequal to about 8 mm, greater than or equal to about 10 mm, greater thanor equal to about 12 mm, greater than or equal to about 15 mm, greaterthan or equal to about 20 mm, greater than or equal to about 25 mm,greater than or equal to 30 mm, or greater than or equal to 40 mm. Insome instances, the fibers may have an average length of less than orequal to about 50 mm, less than or equal to about 40 mm, less than orequal to about 30 mm, less than or equal to about 25 mm, less than orequal to about 20 mm, less than or equal to about 15 mm, less than orequal to about 12 mm, less than or equal to about 10 mm, less than orequal to about 8 mm less than or equal to about 7 mm, less than or equalto about 5 mm, less than or equal to about 3 mm, less than or equal toabout 2 mm, or less than or equal to about 1.5 mm. Combinations of theabove-referenced ranges are also possible (e.g., greater than or equalto about 1 mm and less than or equal to about 50 mm, greater than orequal to about 1 mm and less than or equal to about 15 mm, greater thanor equal to about 1.5 mm and less than or equal to about 30 mm,). Othervalues of average fiber length are also possible.

The support layer, as described herein, may have certain structuralcharacteristics, such as basis weight, and thickness. For instance, insome embodiments, the support layer may have a basis weight of greaterthan or equal to about 3 g/m², greater than or equal to about 10 g/m²,greater than or equal to about 22 g/m², greater than or equal to about25 g/m², greater than or equal to about 30 g/m², greater than or equalto about 33 g/m², greater than or equal to about 40 g/m², greater thanor equal to about 50 g/m², greater than or equal to about 60 g/m²,greater than or equal to about 70 g/m², greater than or equal to about80 g/m², greater than or equal to about 100 g/m², greater than or equalto about 200 g/m², greater than or equal to about 300 g/m², or greaterthan or equal to about 400 g/m². In some instances, the support layermay have a basis weight of less than or equal to about 500 g/m², lessthan or equal to about 400 g/m², less than or equal to about 300 g/m²,less than or equal to about 200 g/m², less than or equal to about 100g/m², less than or equal to about 90 g/m², less than or equal to about80 g/m², less than or equal to about 70 g/m², less than or equal toabout 60 g/m², less than or equal to about 50 g/m², less than or equalto about 40 g/m², less than or equal to about 33 g/m², less than orequal to about 30 g/m², or less than or equal to about 25 g/m².Combinations of the above-referenced ranges are also possible (e.g., abasis weight of greater than or equal to about 22 g/m² and less than orequal to about 90 g/m², a basis weight of greater than or equal to about33 g/m² and less than or equal to about 70 g/m², a basis weight ofgreater than or equal to about 3 g/m² and less than or equal to about500 g/m²). Other values of basis weight are also possible. The basisweight may be determined according to the standard ASTM D-846.

The thickness of the support layer may be selected as desired. Forinstance, in some embodiments, the support layer may have a thickness ofgreater than or equal to about 0.01 mm, greater than or equal to about0.1 mm, greater than or equal to about 0.2 mm, greater than or equal toabout 0.3 mm, greater than or equal to about 0.4 mm, greater than orequal to about 0.5 mm, greater than or equal to about 1.0 mm, greaterthan or equal to about 1.5 mm, greater than or equal to about 2 mm,greater than or equal to about 3 mm, or greater than or equal to about 4mm. In some instances, the support layer may have a thickness of lessthan or equal to about 5 mm, less than or equal to about 4 mm, less thanor equal to about 3 mm, less than or equal to about 2 mm, less than orequal to about 1.2 mm, less than or equal to about 0.5 mm, less than orequal to about 0.4 mm, less than or equal to about 0.3 mm, less than orequal to about 0.2 mm, or less than or equal to about 0.1 mm.Combinations of the above-referenced ranges are also possible (e.g., athickness of greater than or equal to about 0.01 mm and less than orequal to about 5 mm, a thickness of greater than or equal to about 0.1mm and less than or equal to about 2 mm). Other values of thickness arealso possible. The thickness may be determined according to the standardTAPPI T411.

The mean flow pore size may be selected as desired. For instance, insome embodiments, the support layer may have a mean flow pore size ofgreater than or equal to about 1 micron, greater than or equal to about5 microns, greater than or equal to about 10 microns, greater than orequal to about 30 microns, greater than or equal to about 50 microns,greater than or equal to about 100 microns, greater than or equal toabout 120 microns, greater than or equal to about 150 microns, greaterthan or equal to about 300 microns, greater than or equal to about 500microns, greater than or equal to about 1000 microns, greater than orequal to about 2000 microns, greater than or equal to about 3000microns, or greater than or equal to about 4000 microns. In someinstances, the support layer may have an average mean flow pore size ofless than or equal to about 5000 microns, less than or equal to about4000 microns, less than or equal to about 3000 microns, less than orequal to about 2000 microns, less than or equal to about 1000 microns,less than or equal to about 500 microns, less than or equal to about 300microns, less than or equal to about 150 microns, less than or equal toabout 120 microns, less than or equal to about 100 microns, less than orequal to about 50 microns, less than or equal to about 30 microns, lessthan or equal to about 10 microns, or less than or equal to about 5microns. Combinations of the above-referenced ranges are also possible(e.g., greater than or equal to about 30 microns and less than or equalto about 150 microns, greater than or equal to about 50 microns and lessthan or equal to about 120 microns). Other values of mean flow pore sizeare also possible. The mean flow pore size may be determined accordingto the standard ASTM E1294 (2008) (M.F.P.).

In some embodiments, the support layer may have a larger mean flow poresize than that of the fiber web.

The filter media described herein (which may optionally include two ormore layers) may have certain structural characteristics such as overallbasis weight. In some embodiments, the filter media may have an overallbasis weight of greater than or equal to about 2 g/m², greater than orequal to about 5 g/m², greater than or equal to about 10 g/m², greaterthan or equal to about 20 g/m², greater than or equal to about 30 g/m²,greater than or equal to about 40 g/m², greater than or equal to about60 g/m², greater than or equal to about 100 g/m², greater than or equalto about 150 g/m², greater than or equal to about 200 g/m², greater thanor equal to about 250 g/m², greater than or equal to about 350 g/m²,greater than or equal to about 500 g/m², greater than or equal to about800 g/m², greater than or equal to about 1000 g/m², greater than orequal to about 2000 g/m², greater than or equal to about 2500 g/m². Insome instances, the filter media may have an overall basis weight ofless than or equal to about 2800 g/m², less than or equal to about 2500g/m², less than or equal to about 2000 g/m², less than or equal to about1000 g/m², less than or equal to about 800 g/m², less than or equal toabout 500 g/m², less than or equal to about 300 g/m², less than or equalto about 200 g/m², or less than or equal to about 100 g/m², less than orequal to about 60 g/m², less than or equal to about 40 g/m², less thanor equal to about 20 g/m², less than or equal to about 10 g/m², or lessthan or equal to about 5 g/m². Combinations of the above-referencedranges are also possible (e.g., greater than or equal to about 40 g/m²and less than or equal to about 2800 g/m², greater than or equal toabout 60 g/m² and less than or equal to about 800 g/m²). Other values ofoverall basis weight are also possible. The overall basis weight may bedetermined according to the standard ASTM D-846.

The overall air permeability of the filter media described herein canvary. In some embodiments, the overall air permeability of the filtermedia may be, for example, greater than or equal to about 0.7 L/m²s,greater than or equal to about 1 L/m²s, greater than or equal to about 5L/m²s, greater than or equal to about 10 L/m²s, greater than or equal toabout 15 L/m²s, greater than or equal to about 25 L/m²s, greater than orequal to about 50 L/m²s, greater than or equal to about 100 L/m²s,greater than or equal to about 150 L/m²s, greater than or equal to about200 L/m²s, greater than or equal to about 250 L/m²s, greater than orequal to about 300 L/m²s, greater than or equal to about 500 L/m²s,greater than or equal to about 700 L/m²s, greater than or equal to about1000 L/m²s, or greater than or equal to about 1200 L/m²s. In someinstances, the overall air permeability of the filter media may be, forexample, less than or equal to about 1500 L/m²s, less than or equal toabout 1200 L/m²s, less than or equal to about 1000 L/m²s, less than orequal to about 700 L/m²s, less than or equal to about 500 L/m²s, lessthan or equal to about 300 L/m²s, less than or equal to about 250 L/m²s,less than or equal to about 200 L/m²s, less than or equal to about 150L/m²s, less than or equal to about 100 L/m²s, less than or equal toabout 50 L/m²s, less than or equal to about 25 L/m²s, less than or equalto about 20 L/m²s, less than or equal to about 15 L/m²s, less than orequal to about 10 L/m²s, less than or equal to about 5 L/m²s, or lessthan or equal to about 1 L/m²s. Combinations of the above-referencedranges are also possible (greater than or equal to about 0.7 L/m²s andless than or equal to about 1500 L/m²s, greater than or equal to about15 L/m²s and less than or equal to about 700 L/m²s). Other ranges ofoverall air permeability are also possible. As determined herein, theoverall air permeability is measured according to standard TAPPI T251(wherein the flow is 10,000 L/m²/s on 20 cm² area). The permeability ofa filter media is an inverse function of flow resistance and can bemeasured with a Frazier Permeability Tester. The Frazier PermeabilityTester measures the volume of air per unit of time that passes through aunit area of media at a fixed differential pressure across the media.

The overall thickness of the filter media may be selected as desired.For instance, in some embodiments, the filter media may have an overallthickness of greater than or equal to about 0.1 mm, greater than orequal to about 0.2 mm, greater than or equal to about 0.3 mm, greaterthan or equal to about 0.4 mm, greater than or equal to about 0.5 mm,greater than or equal to about 1.0 mm, greater than or equal to about1.5 mm, greater than or equal to about 2 mm, greater than or equal toabout 5 mm, greater than or equal to about 10 mm, greater than or equalto about 20 mm, greater than or equal to about 30 mm, or greater than orequal to about 40 mm. In some instances, the filter media may have anoverall thickness of less than or equal to about 50 mm, less than orequal to about 40 mm, less than or equal to about 30 mm, less than orequal to about 20 mm, less than or equal to about 10 mm, less than orequal to about 5 mm, less than or equal to about 2.0 mm, less than orequal to about 1.2 mm, less than or equal to about 0.5 mm, less than orequal to about 0.4 mm, less than or equal to about 0.3 mm, or less thanor equal to about 0.2 mm. Combinations of the above-referenced rangesare also possible (e.g., a thickness of greater than or equal to about0.01 mm and less than or equal to about 50 mm, a thickness of greaterthan or equal to about 0.1 mm and less than or equal to about 30 mm).Other values of overall thickness are also possible. The thickness maybe determined according to the standard TAPPI T411.

The filter media, filter element, fiber web and/or support layer mayalso include other components, such as a binder resin, surfacetreatments, and/or additives. In general, any suitable binder resin maybe used to achieve the desired properties. For example, the binder resinmay be polymeric, water-based, or solvent-based. In certain embodiments,the binder resin may also include additives.

In some embodiments, the fiber web and/or the support layer of a filtermedia described herein include a binder resin. Typically, a binder resinor any additional components, if present, are present in limitedamounts. In some embodiments, the fiber web and/or the support layer mayinclude wet and/or dry strength binder resins that include, for example,natural polymers (starches, gums), cellulose derivatives, such ascarboxymethyl cellulose, methylcellulose, hemicelluloses, syntheticpolymers such as phenolics, latexes, polyamides, polyacrylamides,urea-formaldehyde, melamine-formaldehyde, polyamides), surfactants,coupling agents, crosslinking agents, and/or conductive additives,amongst others. In some embodiments, the binder resin may comprise athermoplastic (e.g., acrylic, polyvinylacetate, polyester, polyamide), athermoset (e.g., epoxy, phenolic resin), or a combination thereof. Insome cases, a binder resin includes one or more of a vinyl acetateresin, an epoxy resin, a polyester resin, a copolyester resin, apolyvinyl alcohol resin, an acrylic resin such as a styrene acrylicresin, and a phenolic resin. Other binder resins are also possible.

The binder resin is generally not in fiber form and is to bedistinguished from binder fiber (e.g., multi-component fiber) describedabove. In general, the binder resin may have any suitable composition.

The amount of binder resin in the fiber web and/or support layer mayvary. For instance, in some embodiments, the weight percentage of binderresin in the fiber web may be greater than or equal to about 0 wt %,greater than or equal to about 2 wt %, greater than or equal to about 5wt %, greater than or equal to about 10 wt %, or greater than or equalto about 15 wt %. In some cases, the weight percentage of binder resinin the fiber web may be less than or equal to about 20 wt %, less thanor equal to about 15 wt %, less than or equal to about 10 wt %, lessthan or equal to about 5 wt %, or less than or equal to about 2 wt %.Combinations of the above-referenced ranges are also possible (e.g., aweight percentage of binder resin of greater than or equal to about 0 wt% and less than or equal to about 20 wt %, a weight percentage of binderresin of greater than or equal to about 2 wt % and less than or equal toabout 15 wt %). Other ranges are also possible.

The binder resin may be added to the fibers in any suitable mannerincluding, for example, in the wet state. In some embodiments, thebinder resin coats the fibers and is used to adhere fibers to each otherto facilitate adhesion between the fibers. Any suitable method andequipment may be used to coat the fibers, and are described in thecontext of coating methods above.

In some embodiments, a binder resin may be added to the fiber web and/orone or more additional layers by a solvent saturation process. Incertain embodiments, a polymeric material can be impregnated into filtermedium either during or after the filter medium is being manufactured ona papermaking machine. For example, after the fiber web is formed, itcan be impregnated with a polymeric material by using a reverse rollapplicator following the just-mentioned method and/or by using a dip andsqueeze method (e.g., by dipping a dried filter media into a polymeremulsion or solution and then squeezing out the excess polymer by usinga nip). A polymeric material can also be applied to the fiber web and/orone or more additional layers by other methods known in the art, such asspraying or foaming. p Fiber webs and/or one or more additional layersfor incorporation into a filter media, as described herein, may beproduced using any suitable processes, such as using a wet laid process(e.g., a process involving a pressure former, a rotoformer, afourdrinier, a hybrid former, inclined wire, or a twin wire process) ora non-wet laid process (e.g., a dry laid process, an air laid process, ameltblown process). In general, a wet laid process involves mixingtogether of fibers of one or more type to provide a fiber slurry. Theslurry may be, for example, an aqueous-based slurry. In certainembodiments, the various fibers are optionally stored separately, or incombination, in various holding tanks prior to being mixed together(e.g., to achieve a greater degree of uniformity in the mixture).

For instance, a first fiber may be mixed and pulped together in onecontainer and a second fiber may be mixed and pulped in a separatecontainer. The first fibers and the second fibers may subsequently becombined together into a single fibrous mixture. Appropriate fibers maybe processed through a pulper before and/or after being mixed together.In some embodiments, combinations of fibers are processed through apulper and/or a holding tank prior to being mixed together. It can beappreciated that other components may also be introduced into themixture.

Any suitable method for creating a fiber slurry may be used. In someembodiments, further additives are added to the slurry to facilitateprocessing. The temperature may also be adjusted to a suitable range,for example, between 33° F. and 100° F. (e.g., between 50° F. and 85°F.). In some cases, the temperature of the slurry is maintained. In someinstances, the temperature is not actively adjusted.

In some embodiments, the wet laid process uses similar equipment as in aconventional papermaking process, for example, a hydropulper, a formeror a headbox, a dryer, and an optional converter. A layer can also bemade with a laboratory handsheet mold in some instances. As discussedabove, the slurry may be prepared in one or more pulpers. Afterappropriately mixing the slurry in a pulper, the slurry may be pumpedinto a headbox where the slurry may or may not be combined with otherslurries. Other additives may or may not be added. The slurry may alsobe diluted with additional water such that the final concentration offiber is in a suitable range, such as for example, between about 0.01%to 0.5% by weight, or between about 0.1% and 0.5% by weight.

In some cases, the pH of the fiber slurry may be adjusted as desired.For instance, fibers of the slurry may be dispersed under generallyneutral conditions.

Before the slurry is sent to a headbox, the slurry may optionally bepassed through centrifugal cleaners and/or pressure screens for removingunfiberized material. The slurry may or may not be passed throughadditional equipment such as refiners or deflakers to further enhancethe dispersion or fibrillation of the fibers. For example, deflakers maybe useful to smooth out or remove lumps or protrusions that may arise atany point during formation of the fiber slurry. Fibers may then becollected on to a screen or wire at an appropriate rate using anysuitable equipment, e.g., a fourdrinier, a rotoformer, a cylinder, or aninclined wire fourdrinier.

In some embodiments, the process involves introducing a binder (and/orother components) into a pre-formed fiber layer. In some embodiments, asthe fiber web is passed along an appropriate screen or wire, differentcomponents included in the binder, which may be in the form of separateemulsions, are added to the fiber web using a suitable technique. Insome cases, each component of the binder resin is mixed as an emulsionprior to being combined with the other components and/or fiber web. Insome embodiments, the components included in the binder may be pulledthrough the fiber web using, for example, gravity and/or vacuum. In someembodiments, one or more of the components included in the binder resinmay be diluted with softened water and pumped into the fiber web. Insome embodiments, a binder may be introduced to the fiber web byspraying onto the formed media, or by any other suitable method, such asfor example, size press application, foam saturation, curtain coating,rod coating, amongst others. In some embodiments, a binder material maybe applied to a fiber slurry prior to introducing the slurry into aheadbox. For example, the binder material may be introduced (e.g.,injected) into the fiber slurry and impregnated with and/or precipitatedon to the fibers. In some embodiments, a binder resin may be added to afiber web by a solvent saturation process.

In other embodiments, a non-wet laid process is used to form fiber web(or one or more additional layers) of a media. For example, in a non-wetlaid process, an air laid process or a carding process may be used. Forexample, in an air laid process, fibers may be mixed while air is blownonto a conveyor, and a binder is then applied. In a carding process, insome embodiments, the fibers are manipulated by rollers and extensions(e.g., hooks, needles) associated with the rollers prior to applicationof the binder. In some cases, forming the layers through a non-wet laidprocess may be more suitable for the production of a highly porousmedia. The non-wet layer may be impregnated (e.g., via saturation,spraying, etc.) with any suitable binder resin, as discussed above.

During or after formation of a fiber web, the fiber web may be furtherprocessed according to a variety of known techniques. Optionally,additional layers can be formed and/or added to a fiber web usingprocesses such as lamination, thermo-dot bonding, ultrasonic,calendering, glue-web, co-pleating, or collation.

In some embodiments, further processing may involve pleating the fiberweb and/or the filter media. For instance, two layers may be joined by aco-pleating process. In some cases, the filter media, or various layersthereof, may be suitably pleated by forming score lines at appropriatelyspaced distances apart from one another, allowing the filter media to befolded. It should be appreciated that any suitable pleating techniquemay be used.

In some embodiments, a filter media can be post-processed such assubjected to a corrugation process to increase surface area within theweb. In other embodiments, a filter media may be embossed.

In some embodiments, as described herein, a fiber web (or one or moreadditional layers) may include fibers formed from a meltblown process.In embodiments in which the filter media includes a meltblown layer, themeltblown layer may have one or more characteristics described incommonly-owned U.S. Patent Publication No. 2009/0120048, entitled“Meltblown Filter Medium”, which is based on U.S. patent applicationSer. No. 12/266,892, filed on May 14, 2009, and commonly-owned U.S.application Ser. No. 12/971,539, entitled “Fine Fiber Filter Media andProcesses”, filed on Dec. 17, 2010, each of which is incorporated hereinby reference in its entirety for all purposes. In other embodiments, afiber web may be formed via other suitable processes such as meltspunprocesses.

The filter media described herein can be incorporated into a variety offilter elements for use in various applications. In some cases, filtermedia described herein can be used as filter media for coalescingapplications (e.g., using a wrapped filter). For example, such filtermedia may be used to remove oil from a gas stream (e.g., a compressedair stream).

In some embodiments, the filter media described herein can beincorporated into a filter element used in hydraulic and/ornon-hydraulic filtration applications. Exemplary uses of hydraulicfilters (e.g., high-, medium-, and low-pressure specialty filters)include mobile and industrial filters. Exemplary uses of non-hydraulicfilters include fuel filters (e.g., ultra-low sulfur diesel), oilfilters (e.g., lube oil filters or heavy duty lube oil filters),chemical processing filters, industrial processing filters, medicalfilters (e.g., filters for blood), air filters (e.g., heavy duty airfilters, automotive air filters, HVAC filters, HEPA filters), and waterfilters. In some embodiments, an external support layer substantiallysupports the filter element, such that an additional support layerand/or a core (e.g., a plastic or metallic net, or wire mesh), is absentfrom the filter media or filter element. In other embodiments, thefilter element may comprise one or more additional support layers and/orcores. In some embodiments, a fiber web of filter media may be wrappedaround a core (e.g., a synthetic or metal core) to form a wrappedfilter, as described herein. The filter elements may have the sameproperty values as those noted above in connection with the filtermedia. For example, the above-noted basis weights, efficiencies of thefilter media may also be found in filter elements.

In some embodiments, as described herein, the fiber webs, filter media,and/or filter elements described herein may be useful in a systemcomprising a device for generating an gas stream. For example, incertain embodiments, the system may comprise the device for generatingan gas stream, and the filter media or filter element positioneddownstream of the device. In certain embodiments, the gas streamcomprises a fluid to be filtered out of the gas stream, such as an oil,lubricant, and/or cooling agent as described herein.

Non-limiting examples of devices for generating an gas stream comprisingoil, lubricant, and/or cooling agent include compressors, distillationcolumns, evaporators, thermal oil ventilators, crankcase ventilators,combustion engines, exhaust conduits, turbines (e.g., gas turbines), andcombinations thereof.

The filter media and filter elements described herein may be useful forpreventing fouling caused by oil, lubricants, cooling agents, and/orother fluids in such systems and devices, including but not limited to,for example, compressors, gas turbines, amine or glycol absorbers,molecular sieves, PSA's, metering stations, mercury guard beds, gasfired heaters or furnaces, heat exchangers and/or gas-gas purificationmembranes. The filter media and filter elements may also be useful inapplications utilizing gas streams comprising an oil, lubricant, and/orcooling agent including, but not limited to, for example: natural gasproduction; blow off gases in the oil and mining industry containingsuspended liquids; gasses from downstream sides of distillation columns;separation of droplets of steam that carried from evaporators; thermaloil ventilation; crankcase ventilation in cars or other combustionsengines (e.g., piston or rotary type engines); exhaust fumes in general;excess gasses from chemical industry; cooling and condensing exhaustfumes from power plants; fog removal in general; blow off gasses fromoil fog lubricated fast rotating machinery; fog generated by the coolingand lubricant liquids from mills, lathes, grinders and other type ofmachines using regular or irregular shaped cutting edges; facemasks(e.g., for personal protection against short time exposure to oil fog);fog generated by evaporating oil in continuous rolling mills; acetylenetorch cutting; plasma cutting; electron beam cutting and all kinds ofelectrical arc welding and cutting; presses (e.g., high speed presses)and die cutters and die forges; downstream of pumps; downstream and/orupstream of vacuum blowers in general; paint or oil spray cabin exhaustair treatment; mixing chambers for liquids; evaporation cooler exhaustair; dry tower exhaust air (e.g., milk powder or similar productscontaining oily or fatty substance); process gasses for welding orcutting; medical applications; food industry process air; pressurizedair controlled control systems; gasses transported in the industry forliquefying gases (e.g., nitrogen, carbon dioxide); inside airconditioning (e.g., HVAC) units to remove droplets from the coolingagent from the gas stream; and heat pipes (e.g., to avoid unwantedtransport of the heat transport liquid from the condenser to theevaporator).

In an exemplary embodiment, a filter element comprises a stainless steelmesh core, two or more fiber webs layers wrapped around the mesh core,and a fibrous support layer comprising synthetic fibers wrapped aroundthe fiber web layers. In another exemplary embodiment, the filterelement comprises a two or more fiber web layers wrapped around afibrous core, and a support layer comprising synthetic fibers wrappedaround the two or more fiber web layers. In yet another exemplaryembodiment, the filter element comprises two or more fiber web layerswrapped around a perforated metal sheet core.

In some embodiments, an inlet may be disposed within the core, such thata gas stream comprising an oil, lubricant, and/or cooling agent passesinto the core, through the filter media including the fiber web layersand support layer(s), and subsequently into an outlet positionedproximate the outer-most layer of the filter media, such that the filterelement has coalesced at least a portion of the oil, lubricant, and/orcooling agent.

In another exemplary embodiment, the filter element comprises two ormore fiber web wrapped layers disposed within a perforated sheet metalcore. In some such embodiments, an inlet of the filter element may bepositioned proximate the external perforated sheet metal core, such thata gas stream comprising an oil, lubricant, and/or cooling agent passesthrough the core into the fiber web layers and subsequently into anoutlet disposed within the filter element, such that the filter elementhas coalesced at least a portion of the oil, lubricant, and/or coolingagent.

Other configurations and combinations of cores, support layers, andfiber webs are also possible.

Other systems, devices, and applications are also possible and thoseskilled in the art would be capable of selecting such systems, devices,and applications based upon the teachings of this specification.

While several embodiments of the present invention have been describedand illustrated herein, those of ordinary skill in the art will readilyenvision a variety of other means and/or structures for performing thefunctions and/or obtaining the results and/or one or more of theadvantages described herein, and each of such variations and/ormodifications is deemed to be within the scope of the present invention.More generally, those skilled in the art will readily appreciate thatall parameters, dimensions, materials, and configurations describedherein are meant to be exemplary and that the actual parameters,dimensions, materials, and/or configurations will depend upon thespecific application or applications for which the teachings of thepresent invention is/are used. Those skilled in the art will recognize,or be able to ascertain using no more than routine experimentation, manyequivalents to the specific embodiments of the invention describedherein. It is, therefore, to be understood that the foregoingembodiments are presented by way of example only and that, within thescope of the appended claims and equivalents thereto, the invention maybe practiced otherwise than as specifically described and claimed. Thepresent invention is directed to each individual feature, system,article, material, kit, and/or method described herein. In addition, anycombination of two or more such features, systems, articles, materials,kits, and/or methods, if such features, systems, articles, materials,kits, and/or methods are not mutually inconsistent, is included withinthe scope of the present invention. The indefinite articles “a” and“an,” as used herein in the specification and in the claims, unlessclearly indicated to the contrary, should be understood to mean “atleast one.”

The phrase “and/or,” as used herein in the specification and in theclaims, should be understood to mean “either or both” of the elements soconjoined, i.e., elements that are conjunctively present in some casesand disjunctively present in other cases. Other elements may optionallybe present other than the elements specifically identified by the“and/or” clause, whether related or unrelated to those elementsspecifically identified unless clearly indicated to the contrary. Thus,as a non-limiting example, a reference to “A and/or B,” when used inconjunction with open-ended language such as “comprising” can refer, insome embodiments, to A without B (optionally including elements otherthan B); in another embodiment, to B without A (optionally includingelements other than A); in yet another embodiment, to both A and B(optionally including other elements); etc.

As used herein in the specification and in the claims, “or” should beunderstood to have the same meaning as “and/or” as defined above. Forexample, when separating items in a list, “or” or “and/or” shall beinterpreted as being inclusive, i.e., the inclusion of at least one, butalso including more than one, of a number or list of elements, and,optionally, additional unlisted items. Only terms clearly indicated tothe contrary, such as “only one of” or “exactly one of,” or, when usedin the claims, “consisting of,” will refer to the inclusion of exactlyone element of a number or list of elements. In general, the term “or”as used herein shall only be interpreted as indicating exclusivealternatives (i.e. “one or the other but not both”) when preceded byterms of exclusivity, such as “either,” “one of,” “only one of,” or“exactly one of.” “Consisting essentially of,” when used in the claims,shall have its ordinary meaning as used in the field of patent law. Asused herein in the specification and in the claims, the phrase “at leastone,” in reference to a list of one or more elements, should beunderstood to mean at least one element selected from any one or more ofthe elements in the list of elements, but not necessarily including atleast one of each and every element specifically listed within the listof elements and not excluding any combinations of elements in the listof elements. This definition also allows that elements may optionally bepresent other than the elements specifically identified within the listof elements to which the phrase “at least one” refers, whether relatedor unrelated to those elements specifically identified. Thus, as anon-limiting example, “at least one of A and B” (or, equivalently, “atleast one of A or B,” or, equivalently “at least one of A and/or B”) canrefer, in some embodiments, to at least one, optionally including morethan one, A, with no B present (and optionally including elements otherthan B); in another embodiment, to at least one, optionally includingmore than one, B, with no A present (and optionally including elementsother than A); in yet another embodiment, to at least one, optionallyincluding more than one, 8 A, and at least one, optionally includingmore than one, B (and optionally including other elements); etc.

In the claims, as well as in the specification above, all transitionalphrases such as “comprising,” “including,” “carrying,” “having,”“containing,” “involving,” “holding,” and the like are to be understoodto be open-ended, i.e., to mean including but not limited to. Only thetransitional phrases “consisting of” and “consisting essentially of”shall be closed or semi-closed transitional phrases, respectively, asset forth in the United States Patent Office Manual of Patent ExaminingProcedures, Section 2111.03.

The term “alkane” is given its ordinary meaning in the art and refers toa saturated hydrocarbon molecule.

The term “amine” is given its ordinary meaning in the art and refers toa primary (—NH₂), secondary (—NHR_(x)), tertiary (—NR_(x)R_(y)), orquaternary (—N⁺R_(x)R_(y)R_(z)) amine (e.g., where R_(x), R_(y), andR_(z) are independently an aliphatic, alicyclic, alkyl, aryl, or othermoieties, as defined herein).

The term “amide” is given its ordinary meaning in the art and refers toa compound containing a nitrogen atom and a carbonyl group of thestructure R_(x)CONR_(y)R_(z) (e.g., where R_(x), R_(y), and R_(z) areindependently an aliphatic, alicyclic, alkyl, aryl, or other moieties,as defined herein).

Any terms as used herein related to shape, orientation, alignment,and/or geometric relationship of or between, for example, one or morearticles, structures, forces, fields, flows, directions/trajectories,and/or subcomponents thereof and/or combinations thereof and/or anyother tangible or intangible elements not listed above amenable tocharacterization by such terms, unless otherwise defined or indicated,shall be understood to not require absolute conformance to amathematical definition of such term, but, rather, shall be understoodto indicate conformance to the mathematical definition of such term tothe extent possible for the subject matter so characterized as would beunderstood by one skilled in the art most closely related to suchsubject matter. Examples of such terms related to shape, orientation,and/or geometric relationship include, but are not limited to termsdescriptive of: shape—such as, round, square, circular/circle,rectangular/rectangle, triangular/triangle, cylindrical/cylinder,elliptical/ellipse, (n)polygonal/(n)polygon, etc.; angularorientation—such as perpendicular, orthogonal, parallel, vertical,horizontal, collinear, etc.; contour and/or trajectory—such as,plane/planar, coplanar, hemispherical, semi-hemispherical, line/linear,hyperbolic, parabolic, flat, curved, straight, arcuate, sinusoidal,tangent/tangential, etc.; direction—such as, north, south, east, west,etc.; surface and/or bulk material properties and/or spatial/temporalresolution and/or distribution—such as, smooth, reflective, transparent,clear, opaque, rigid, impermeable, uniform(ly), inert, non-wettable,insoluble, steady, invariant, constant, homogeneous, etc.; as well asmany others that would be apparent to those skilled in the relevantarts. As one example, a fabricated article that would described hereinas being “ square” would not require such article to have faces or sidesthat are perfectly planar or linear and that intersect at angles ofexactly 90 degrees (indeed, such an article can only exist as amathematical abstraction), but rather, the shape of such article shouldbe interpreted as approximating a “ square,” as defined mathematically,to an extent typically achievable and achieved for the recitedfabrication technique as would be understood by those skilled in the artor as specifically described. As another example, two or more fabricatedarticles that would described herein as being “ aligned” would notrequire such articles to have faces or sides that are perfectly aligned(indeed, such an article can only exist as a mathematical abstraction),but rather, the arrangement of such articles should be interpreted asapproximating “aligned,” as defined mathematically, to an extenttypically achievable and achieved for the recited fabrication techniqueas would be understood by those skilled in the art or as specificallydescribed.

What is claimed is:
 1. A method for filtering an oil, lubricant, and/orcooling agent from a gas stream, the method comprising: passing the gasstream including the oil, lubricant, and/or cooling agent through afilter element, wherein the filter element comprises a fiber web wrappedaround a core such that at least two layers of the fiber web are formed,the fiber web comprising: a plurality of fibers having an average fiberdiameter of at least 0.01 microns and less than or equal to 50 microns;a basis weight of at least 1 g/m² and less than or equal to 270 g/m²;and a thickness of at least 0.01 mm and less than or equal to 5.0 mm,wherein the fiber web has an oil repellency level of between 4 and 6;wherein the fiber web has an oil carry over of less than 20%, andwherein the oil, lubricant, and/or cooling agent has a surface tensionof between 22 mN/m and 33 mN/m measured at 23° C. and 50% RH.
 2. Amethod for filtering an oil, lubricant, and/or cooling agent from a gasstream, the method comprising: passing the gas stream including the oil,lubricant, and/or cooling agent through a fiber web, wherein the fiberweb comprises: a plurality of fibers having an average fiber diameter ofat least 0.01 microns and less than or equal to 50 microns; a basisweight of at least 1 g/m² and less than or equal to 270 g/m²; and athickness of at least 0.01 mm and less than or equal to 5.0 mm, whereinthe fiber web has an oil repellency level of between 4 or greater and 6or less, and wherein the fiber web comprises a plurality of perforationshaving an average cross-sectional dimension of at least about 1 mm.
 3. Amethod as in claim 1, wherein the oil, lubricant, and/or cooling agenthas a surface tension of between 22 mN/m and 33 mN/m measured at 23° C.and 50% RH.
 4. A method as in claim 1, wherein the gas stream isgenerated by a compressor, natural gas production equipment, adistillation column, an evaporator, a thermal oil ventilator, acrankcase ventilator, a combustion engine, and/or an exhaust conduit. 5.A filter element, comprising: a core; and a fiber web wrapped around thecore such that at least two layers of the fiber web are formed, whereinthe fiber web comprises: a plurality of fibers having an average fiberdiameter of at least 0.01 microns and less than or equal to 50 microns;a basis weight of at least 1 g/m² and less than or equal to 270 g/m²;and a thickness of at least 0.01 mm and less than or equal to 5.0 mm,wherein the fiber web has an oil repellency level of between 4 orgreater and 6 or less, and wherein the fiber web has an oil carry overof less than 20%.
 6. A filter element as in claim 5, wherein the corecomprises a wire mesh.
 7. A filter media, comprising: a fiber web,wherein the fiber web comprises: a plurality of fibers having an averagefiber diameter of at least 0.01 microns and less than or equal to 50microns; a basis weight of at least 1 g/m² and less than or equal to 270g/m²; and a thickness of at least 0.01 mm and less than or equal to 5.0mm, wherein the fiber web has an oil repellency level of between 4 orgreater and 6 or less, and wherein the fiber web comprises a pluralityof perforations having an average cross-sectional dimension of at leastabout 1 mm.
 8. A filter element as in claim 5, wherein the filterelement or filter media comprises a support layer.
 9. A filter elementas in claim 8, wherein the support layer comprises a plurality offibers.
 10. A method as in claim 1, wherein a weight percentage ofbinder fibers present in the fiber web is at least about 0 wt % and lessthan or equal to about 10 wt %.
 11. A method as in claim 1, wherein thefiber web comprises glass fibers, wherein the weight percentage of glassfibers present in the fiber web is greater than or equal to about 0% andless than or equal to about 99% by weight of the total fibers in thefiber web.
 12. A method as in claim 1, wherein the fiber web comprisessynthetic fibers, wherein the weight percentage of synthetic fiberspresent in the web is greater than or equal to about 1% and less than orequal to about 100% by weight of the total fibers in the fiber web. 13.A method as in claim 1, wherein the fiber web comprises cellulosefibers, wherein the weight percentage of cellulose fibers present in thefiber web is greater than or equal to about 1% and less than or equal toabout 100% by weight of the total fibers in the fiber web.
 14. A methodas in claim 1, wherein the fiber web has at least one modified surface.15. A method as in claim 1, wherein at least one surface of the fiberweb is coated with a coating.
 16. A method as in claim 15, wherein thecoating comprises a fluorinated polymer.
 17. A method as in claim 1,wherein the fiber web has an initial efficiency of greater than or equalto about 1% and less than or equal to about 99.99%.
 18. A systemcomprising the filter element of claim 5, wherein the filter element ispositioned downstream of a device for generating a gas stream includingan oil, lubricant, and/or cooling agent, wherein the oil, lubricant,and/or cooling agent has a surface tension of between 22 mN/m and 33mN/m measured at 23° C. and 50% RH.
 19. A system as in claim 18, whereinthe device comprises a compressor, a distillation column, an evaporator,a thermal oil ventilator, a crankcase ventilator, a combustion engine,and/or an exhaust conduit.